CN100568549C - Nitride semiconductor photogenerator - Google Patents

Nitride semiconductor photogenerator Download PDF

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CN100568549C
CN100568549C CNB2005101267129A CN200510126712A CN100568549C CN 100568549 C CN100568549 C CN 100568549C CN B2005101267129 A CNB2005101267129 A CN B2005101267129A CN 200510126712 A CN200510126712 A CN 200510126712A CN 100568549 C CN100568549 C CN 100568549C
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CN1790761A (en
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中村修二
长滨慎一
岩佐成人
清久裕之
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Nichia Chemical Industries Ltd
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Abstract

A kind of nitride semiconductor photogenerator has the active layer (14) of a single quantum or multi-quantum pit structure, and it is made of the nitride-based semiconductor that contains indium and gallium.A P type cover layer (61) that is made of the P type nitride-based semiconductor that contains aluminium plus gallium is set up with a face of active layer and contacts.The 2nd a P type cover layer (62) that is made of the P type nitride-based semiconductor that contains aluminium plus gallium is set on the P type cover layer.The 2nd P type cover layer has the big band gap of band gap that covers than a P type.A n type semiconductor layer (13) setting contacts with the another side of active layer (14).

Description

Nitride semiconductor photogenerator
The application is Chinese patent application 02142888.3 (original female case application number: dividing an application 95117565.3).
Technical field
The present invention relates to a kind of light emitting semiconductor device, such as light-emitting diode (LED) or laser diode (LD), particularly a kind of have a luminescent device that is formed semiconductor structure by all nitride semi-conductor materials.
Background technology
As being used for luminescent device, such as the hope emission from ultraviolet light to red range light LED or the material of LD device, be nitride semi-conductor material (In as everyone knows xAl yGa 1-x-yN; 0≤X, 0≤Y, X+Y≤1), and blue streak and blue green light LED for example have been actually used in display or the annunciator.
Photophore light such as the blue streak LED that is formed by nitride semi-conductor material or blue green light LED and actual use at present has double-heterostructure, this luminescent device essential structure is such, the n-type contact layer of forming by n type GaN, the n-type cover layer of forming by n-type AlGaN, the n-type active layer of forming by n-type InGaN, the p-type cover layer of forming by p type AlGaN, p-type cover layer of forming by p-type AlGaN and the p-type contact layer of forming by p-type GaN, by above-mentioned order, be layered on the substrate of making by for example sapphire and make.This active layer is mixed with donor impurity, such as Si or G, and/or mixes with acceptor impurity, such as Mn or Mg.The light emission wavelength of LED device can be by the In content in the InGaN component that changes active layer, or change and be mixed with the kind of source region impurity and change to red light district from ultraviolet region.The LED of practical application at present is that a kind of emission wavelength is the following LED of 510nm, and its active layer is mixed with the alms giver and is subjected to main two kinds of impurity.This LED also have be between substrate and the n-type contact layer for example by GaN or the formed resilient coating of AlN.
On the other hand, up to now, to the existing many suggestions of the structure of LD device.For example, unexamined Japanese Patent Application Publication (KoKai) 6-21511 has disclosed a kind of separation constraints type LD, this LD has a kind of such structure, wherein active layer of being made up of InGaN and thickness are no more than 100 dusts, be inserted between n-type GaN layer and the p-type GaN layer, the composite construction of gained also further is clipped between a n-type AlGaN layer and the p-type AlGaN layer.Two AlGaN layers play a kind of smooth restraint layer.
Realization by the double-heterostructure in the aforesaid LED device can improve luminous output, thereby makes that the LED device is actual to be used.Yet, because this kind LED devices use is mixed InGaN layer with impurity as active layer, this LED device has a kind of shortcoming, the half-band width that is its emission spectrum broadens inevitably, for example, the full color display of adorning the LED device with wide semibelt width luminous spectrum can present a kind of slightly with white emission light, thereby its color rendering zone is narrowed down.
As for the LD device, comprise by, as in the above-mentioned double-heterostructure of not examining the active layer that Japanese Patent Application Publication 6-21511 number described non-doping InGaN form, can realize laser generation in theory, but this double-heterostructure still can not obtain laser generation.People wish that patent application discloses described a kind of quantum well structure and improves emission output greatly as this part by active layer is become.But before the LD device can practical application, it was to be solved to also have many problems to have, such as the problems such as preparation of optical resonance face or optics restraint layer.
For practical LD device, its active layer will present a kind of sharp-pointed and strong taking to can be with emission.Even the LED device also can obtain the emission spectra of narrow half-band width, this will can be with the condition that is emitted as can realize taking to.Yet, the active layer thickness of conventional LED device is quite thick, i.e. 0.1 to 0.2 μ m, therefore the InGaN thickness of heterogeneous outer also growth has just surpassed critical thickness on the AlGaN layer, can be with emission so can not go to realize sharp and strong the taking to of heavily fortified point with the LED device of routine.Promptly can not realize laser generation.Simultaneously,, thereby make the LED device form quantum well structure, might obtain the strong emission of being with if made 1 yuan of layer attenuation greatly like that for shown in the above-mentioned unexamined Japanese patent application 6-21511., if make the thickness attenuation of active layer, then the effect of contraction to light can become deficiency, so make it can't realize laser generation.
Summary of the invention
So first purpose of the present invention provides a kind of energy and produces the nitride semiconductor photogenerator of good laser generation.
Second purpose of the present invention provides a kind of can presenting and improves the nitride semiconductor photogenerator that emission is exported.
To make these and other purposes become clearer from following detailed, this nitride semiconductor photogenerator according to the present invention comprises:
One active layer of one quantum well structure comprises the nitride-based semiconductor that contains indium and gallium, and has first and second first type surfaces;
One the one p-type cover layer comprises that one contains the p-type nitride-based semiconductor of aluminium plus gallium, and provides with second first type surface of this active layer and contact;
The 2nd p-type cover layer comprises that one contains aluminium plus gallium and band gap greater than the tectal p-type of p-type nitride-based semiconductor, and is arranged on the p-type cover layer; And
One n type semiconductor layer contacts with first first type surface of active layer.
According to the present invention, a kind of nitride semiconductor photogenerator also is provided, comprising:
One active layer is made up of a quantum well structure, and it comprises that one contains the nitride-based semiconductor of indium and gallium, and has first and second first type surfaces;
The one n-type cover layer is made of a n-type nitride-based semiconductor that contains aluminium plus gallium or a n-type GaN, and provides with this first first type surface of this active layer and contact, and a n-type overcoat thicknesses range is in 10 dust to 1.0 μ m;
The 2nd n-type cover layer comprises a band gap greater than the tectal n-type of n-type nitride-based semiconductor, and is arranged on the n-type cover layer; And
One p-type semiconductor layer contacts with this first first type surface of this active layer.
According to the present invention, a kind of nitride semiconductor photogenerator also is provided, comprising:
The active layer of one quantum well structure comprises the nitride-based semiconductor that contains indium and gallium, and has first and second first type surfaces;
The one n-type cover layer is made of n-type nitride-based semiconductor that contains aluminium plus gallium or n-type GaN, and is arranged to contact with this first first type surface of this active layer;
The 2nd n-type cover layer comprises that one has band gap greater than the tectal n-type of n-type nitride-based semiconductor, and makes it to be arranged on the n-type cover layer;
The one p-type cover layer comprises that one contains the p-type nitride-based semiconductor of aluminium plus gallium, and is arranged to contact with this second first type surface of this active layer; And
The 2nd p-type cover layer comprises that one contains the n-type nitride-based semiconductor of aluminium plus gallium, and it has greater than the tectal band gap of a p-type, and makes it to be arranged on the p-type cover layer.
According to the present invention, a kind of nitride semiconductor photogenerator also is provided, comprise: the active layer of a quantum well structure, it comprise one contain the nitride-based semiconductor of indium and gallium and be inserted in a n-type nitride semiconductor layer and a p-type semiconductor layer between, this p-type semiconductor layer comprises to be arranged to and the contacted p-type of active layer cover layer, and this p-type cover layer comprises that again one contains the p-type nitride-based semiconductor of aluminium plus gallium and has thickness in 10 dust to 1.0 mu m ranges.
According to the present invention, a kind of nitride semiconductor photogenerator also is provided, comprise: one assigns into the active layer of the quantum well structure of a n-type nitride semiconductor layer and a n-N-type semiconductor N interlayer, this active layer comprises that one contains the nitride-based semiconductor of indium and gallium, and is provided with the trap layer that a thickness is not more than 70 dusts.
According to the present invention, a kind of nitride semiconductor photogenerator also is provided, comprising: one have first and second first type surfaces quantum well structure active layer and comprise that one contains the nitride-based semiconductor of indium and gallium; And the one n-type cover layer comprise that one contains the nitride-based semiconductor of indium and gallium.
According to the present invention, a kind of nitride semiconductor photogenerator also is provided, comprising: one have first and second first type surfaces quantum well structure active layer and comprise that one contains the nitride-based semiconductor of indium and gallium; And the one p-type cover layer comprise that one contains the p-type nitride-based semiconductor of indium and gallium.
According to the present invention, a kind of nitride semiconductor photogenerator also is provided, comprising:
One active layer comprises that one contains the nitride-based semiconductor of indium and gallium, and has first and second first type surfaces;
The one n-type cover layer comprises that one does not contain the n-type nitride-based semiconductor of aluminium, and makes it to be arranged to contact with first first type surface of this active layer; And
One p-type cover layer comprises a p-type nitride-based semiconductor and has a surf zone that this surf zone comprises that one contains the p-type nitride-based semiconductor of aluminium plus gallium at least, and this p-type cover layer is arranged to contact with this second first type surface of this active layer.
According to the present invention, a kind of nitride semiconductor photogenerator also is provided, comprising: one comprises the active layer of the semi-conductive quantum well structure of mononitride; One negative electrode; One positive electrode; Set being set to and the contacted n-type GaN contact layer of negative electrode; And set being set to and the contacted p-type GaN contact layer of this positive electrode.
According to the present invention, a kind of nitride semiconductor photogenerator also is provided, comprising: an active layer has first and second first type surfaces, and comprises that one contains the nitride-based semiconductor of indium and gallium; And a n-type cover layer, comprise the n-type nitride-based semiconductor that contains indium and gallium, have the band gap also bigger, and be set to contact with first first type surface of this active layer than this active layer.
According to the present invention, a kind of nitride semiconductor photogenerator also is provided, comprising: an active layer has first and second first type surfaces and comprises that one contains the nitride-based semiconductor of indium and gallium; And the one p-type cover layer comprise that one contains the p-type nitride-based semiconductor of indium and gallium, have the band gap also bigger, and be set to contact with second first type surface of this active layer than this active layer.
According to the present invention, a kind of nitride semiconductor photogenerator also is provided, comprising:
One active layer comprises that one contains the nitride-based semiconductor of indium and gallium, and has first and second first type surfaces;
The one n-type cover layer comprises that one contains the n-type nitride-based semiconductor of indium and gallium, has the band gap bigger than the band gap of this active layer, and is set to contact with first first type surface of this active layer;
The one p-type cover layer comprises that one contains the p-type nitride-based semiconductor of indium and gallium, has the band gap bigger than the band gap of this active layer, and is set to contact with second first type surface of this active layer;
The 2nd n-type cover layer comprises that one contains the n-type nitride-based semiconductor of aluminium plus gallium, has than the bigger band gap of the tectal band gap of a n-type, and is arranged to contact with a n-type cover layer; And
The 2nd p-type cover layer comprises that one contains the p-type nitride-based semiconductor of aluminium plus gallium, has than the bigger band gap of the tectal band gap of a p-type, and is arranged on the p-type cover layer.
According to the present invention, a kind of nitride semiconductor photogenerator also is provided, comprise an active layer, it comprises the nitride-based semiconductor that contains indium at least, and be inserted between one the one n-type cover layer and one the one p type cover layer, a n type cover layer is made of n-type nitride-based semiconductor, and its thermal coefficient of expansion is less than the thermal coefficient of expansion of active layer, the one p type cover layer is made of p-type nitride-based semiconductor, and its thermal coefficient of expansion is less than the thermal coefficient of expansion of active layer;
Wherein, this active layer has a single quantum or a multi-quantum pit structure, thereby launches a kind of light of the energy also lower than the intrinsic band-gap energy of the nitride-based semiconductor that forms this active layer.
According to the present invention, a kind of nitride semiconductor photogenerator also is provided, comprising: one contains the n-type nitride-based semiconductor of indium or a n-type cover layer of being made by a n-type GaN by one; And one active layer comprise that one contains the nitride-based semiconductor of indium, have than the also big thermal coefficient of expansion of the tectal thermal coefficient of expansion of a n-type and be arranged to contact with a n-type cover layer, wherein, this active layer has a single quantum or has multi-quantum pit structure, thereby launches a kind of light of the energy also lower than the intrinsic band-gap energy of this nitride-based semiconductor that forms this active layer.
According to the present invention, a kind of nitride semiconductor photogenerator also is provided, comprising: an active layer comprises that one contains the nitride-based semiconductor of indium; And the one p-type cover layer comprise that one contains the p-type nitride-based semiconductor of aluminium, have than the also big thermal coefficient of expansion of the thermal coefficient of expansion of this active layer and be arranged to contact with this active layer, wherein, this active layer has a single quantum or has multi-quantum pit structure, thereby launches the light of the energy lower than the intrinsic band-gap energy of this nitride-based semiconductor that forms this active layer.
Description of drawings
Fig. 1 is the profile that schematically illustrates the luminescent device structure of the 1st embodiment according to the present invention;
Fig. 2 is the profile that schematically illustrates the luminescent device structure of the 2nd embodiment according to the present invention;
Fig. 3 is the profile that schematically illustrates the luminescent device structure of the 3rd embodiment according to the present invention;
Fig. 4 is the tectal thickness of a p-type of expression the 1st embodiment according to the present invention and the relation curve between the emission output;
Fig. 5 is the tectal thickness of a n-type of expression the 2nd embodiment according to the present invention and the relation curve between the emission output;
Fig. 6 is the relation curve between expression trap layer thickness and the emission output;
Fig. 7 is the relation curve between expression barrier layer thickness and the emission output;
Fig. 8 is that the luminescent device of expression and routine compares the output chart of luminescent device of the present invention;
Fig. 9 is the profile that schematically illustrates the luminescent device structure of the 4th embodiment according to the present invention;
Figure 10 is the profile that schematically illustrates the luminescent device structure of the 5th embodiment according to the present invention;
Figure 11 is the profile that schematically illustrates the luminescent device structure of the 6th embodiment according to the present invention;
Figure 12 is the profile that schematically illustrates luminescent device structure according to another embodiment of the invention;
Figure 13 is the oblique view of Figure 12 structure;
Figure 14 is the profile that schematically illustrates the luminescent device structure of the 7th embodiment according to the present invention;
Figure 15 is the profile that schematically illustrates according to the present invention again the luminescent device structure of another embodiment;
Figure 16 is the profile that schematically illustrates the luminescent device structure of the 8th embodiment according to the present invention; And
Figure 17 is the relation curve of expression trap layer thickness and emission peak wavelength.
Embodiment
In the following description, sometimes In xGa 1-xN (0＜x＜1) abbreviates InGaN as.Equally, sometimes, Al YGa 1-YN (0＜Y＜1) abbreviates AlGaN as.
According to the first embodiment of the present invention, a kind of nitride semiconductor photogenerator is provided, it is provided with the active layer that is inserted between n-type nitride semiconductor layer and p-type nitride semiconductor layer, this active layer is formed by the nitride-based semiconductor that contains indium and gallium, and constitutes quantum well structure (single quantum well or multi-quantum pit structure).As from the active layer side, above-mentioned p-type nitride semiconductor layer comprises a p-type cover layer that is formed by the p-type nitride-based semiconductor that contains aluminium plus gallium, and the 2nd p-type cover layer, it has than the also big band gap of the tectal band gap of a p-type with by the p-type nitride-based semiconductor that contains aluminium plus gallium and forms.
Fig. 1 schematically illustrates the profile of luminescent device (LD) structure according to first embodiment of the invention.With reference to Fig. 1, this luminescent device comprises a substrate 11, by following order stacked thereon be n-type contact layer 12, n-type cover layer 13, active layer 14, the one p-type cover layers, 61, the two p-type cover layers 62 and p-type contact layer 15.On p-type contact layer 15 surfaces, make the current-limiting layer of making by insulating material and wherein formed opening 16a.Form the positive electrode (p-electrode) 17 that is connected with p-type contact layer 15 by opening 16a again on the surface of this current-limiting layer 16.On the other hand, on n-type contact layer 12, form negative electrode (n-electrode) 18.Also can on this p-type contact layer 15, directly form positive electrode 17 under the situation of LED device, and need not to form current-limiting layer 16.
This substrate 11 can be by sapphire (comprising C-plane, R-plane and A-plane thereof), SiC (comprising 6H-SiC and 4H-SiC), Si, ZnO, GaAs, spinelle (MgAl 2O 4, (111) plane particularly), and can adopt lattice constant to make near the monocrystalline nitride of nitride-based semiconductor.Wherein, adopt sapphire and SiC usually.Although resilient coating does not specifically illustrate in Fig. 1,, for the purpose of the lattice constant mismatch that relaxes these materials, often between substrate and nitride-based semiconductor, form the GaN of thick hundreds of approximately dusts or the resilient coating of AlN.Yet, if substrate is formed near the SiC or the ZnO of nitride-based semiconductor by lattice constant very much, thereby can save resilient coating, so this resilient coating is not shown in Fig. 1.
N-type contact layer 12 can be formed by n-type nitride-based semiconductor, if it is formed by binary or ternary mixed crystal such as GaN or AlGaN, just can obtain good crystalline contact layer.Especially if n-type contact layer 12 is formed by GaN, then can reach with negative electrode material has good Ohmic contact.By donor impurity such as Si, Ge or S etc. are mixed contact layer, just can obtain preferred n-type conductivity.As for the material that is used for negative electrode 18, it then is preferred using the metal material that contains Ti and Au or Ti and Al.
This n-type cover layer 13 can be formed by p-type nitride-based semiconductor, if it just can obtain good crystalline cover layer by forming such as binary such as GaN, AlGaN or InGaN or ternary mixed crystal.Especially if n-type cover layer 13 is formed by InGaN or GaN, then may make the active layer 14 that forms relative thin, thereby can realize the active layer of single quantum well (SQW) or Multiple Quantum Well (MQW) structure, thus the output that improves this luminescent device greatly.Can also save the n-type cover layer 13 of LED device.Concerning the LED device, be necessary to form thickness at 10 dusts to 1.0 μ m, be preferably the n-type cover layer 13 of 30 dusts, and concerning the LD device, then thickness range is from 100 dust to 1.0 μ m to 0.1 μ m.
This active layer 14 preferably should be formed by the InGaN (not mixing impurity) of non-doping, thereby allows can be with emission by taking to, and obtains the emission light of 660nm to 365nm.Has the good crystalline InGaN that is enough to be thinned to the thickness that single quantum well or multi-quantum pit structure can be provided in order to make, very preferably form an InGaN layer in advance as n type cover layer, the band gap of this InGaN layer is than the band gap of the active layer 14 of growth is also big thereon subsequently.
When active layer 14 has SQW or MQW structure, just can obtain the very device of high emission output.Expression formula by SQW and MQW structure means, from the structure of the active layer In by non-doping xGa 1-xThe N compound can obtain the light emission between quantum level.For example, by by unification compound In xGa 1-xThe individual layer (trap layer) that N (0＜x＜1) forms constitutes the active layer of SQW structure, and clips this cover layer 13 and the 61 formation barrier layers of active layer.As this In xGa 1-xThe thickness of N layer is 100 dusts or when following, this active layer is subjected to plastic deformation, thereby enables to obtain the strong light emission between quantum level.On the other hand, the active layer of this MQW structure is to be formed by trap layer and the alternately laminated accumulation of barrier layer.Trap layer and barrier layer can by on composition by the In that differs from one another xGa 1-xN layer (x can from 0 to 1) in the case, is formed.In the active layer of MQW structure, the outermost double-layer films of active layer constitutes the trap layer.When this active layer have-when SQW or MQW structure, just can obtain the about 365nm of wave-length coverage to 660nm, the LED of photoemissive high output visible light between quantum level.When the trap layer thickness of quantum well structure is not more than 70 dusts, when preferably being not more than 50 dusts, can obtain the luminescent device of high emission output.This shows that just the magnitude of its thickness is not more than the critical thickness of InGaN active layer.Because the Bohr radius of electronics is about 30 dusts among the InGaN, when thickness when 70 dusts are following, just can obtain the quantum effect of InGaN.
Equally, with regard to multi-quantum pit structure, preferably the thickness of trap layer is adjusted to 70 dusts or following, and the thickness of barrier layer is adjusted to 150 dusts or following.
Then, will illustrate that also first embodiment of the invention has a distinctive p-type cover layer 61 as follows.
This p-type cover layer 61 is to be formed by the p-type nitride-based semiconductor that contains Al and Ga, and is preferably formed by the ternary mixed crystal of AlGaN.The one p-type cover layer 61 plays light waveguide-layer in the LD device.That is, under the situation of the LD device of the 1st embodiment according to the present invention,, will become and be not enough to light is limited in the active layer 14 if the thickness of active layer 14 is done enough thin so that quantum well structure to be provided.So it is for making it play a kind of light waveguide-layer that limits light that this layer p-type coating 61 is set.In addition, the AlGaN layer is the most desirable, because it can make the p-type layer of high current-carrying concentration at an easy rate, meanwhile, with other kinds of nitride-based semiconductor relatively, be suitable for enlarging its with respect to InGaN active layer 14 can be be offset or refraction coefficient aspect difference.In addition, compare with other kinds of nitride-based semiconductor, at its growing period, p-type AlGaN is not easy to be decomposed, thereby has the effect that the InGaN that stops active layer decomposes when for example resembling with MOVPE method growth AlGaN, therefore, can obtain the active layer of excellent in crystallinity, so improve its output.In this case, a p-type cover layer preferably should be made by AlGaN.On the other hand, if a p-type cover layer is formed by p-type GaN, then emission output will be reduced to 1/3 when adopting p-type AlGaN.The reason of this phenomenon can be tied in such fact, compares with AlGaN, and the possibility that GaN is transformed into the p-type is little, and GaN most likely is decomposed when it is grown, and its crystallinity is degenerated, but details is still unclear.
The thickness of a p-type layer 61 of being made by p-type AlGaN more preferably should be 10
Figure C20051012671200141
Scope to 1.0 μ m is preferably in 10
Figure C20051012671200142
To 0.5 mu m range.If a p-type cover layer 61 is thinner than 10
Figure C20051012671200143
Will lose because a p-type is tectal and have resulting any advantage, cause active layer to decompose, so cause the decline of emission output.On the other hand, if a p-type cover layer is thicker than 1.0 μ m, then a p-type cover layer 61 probably can form crackle, makes it be difficult to form satisfied device.
Particularly under the situation of LD device, a p-type overburden cover should be taken at 100 dusts in 1.0 mu m ranges, is preferably in 100 dusts in 0.5 mu m range.If a p-type cover layer 61 is thinner than 100 dusts, will lose its function as light waveguide-layer.On the other hand, if 61 to 1.0 μ m are also thick for a p-type cover layer, probably can form crackle at a p-type cover layer 61, thereby under forming on the layer at this existing crackle during one deck, its crystallinity of resulting semiconductor layer is just bad, thereby reduces the output of resultant device widely.So with regard to the LD device, the THICKNESS CONTROL of a p-type cover layer 61 is very important.
The 2nd P-type cover layer 62 is formed by its band gap that contains Al and Ga P type nitride-based semiconductor also wideer than the band gap of a P type cover layer 61.The 2nd P type cover layer preferably forms, because then can obtain the P type layer of high carrier concentration easily if P-type AlGaN constitutes thus by P type AlGaN ternary mixed crystal.In addition, the 2nd P type cover layer 62 just can increase difference in band gap and refractive index between the 2nd a P type cover layer 62 and the P-type covering 61, thereby allow the 2nd P type cover layer 62 can play the effect of light limiting layer effectively if P type AlGaN constitutes thus.Thickness to the 2nd P type cover layer 62 is not particularly limited, but in order to obtain the P type AlGaN layer of high carrier concentration and flawless high-crystal quality, its thickness preferably is selected in about 500
Figure C20051012671200151
The scope of～1 μ m.In crystal growth step, with acceptor impurity such as Mg, Zn, C, Be, Ca or Ba doped nitride semiconductor, can obtain P type guide card, if obtain the P type layer of high carrier concentration, mix be subjected to leading matter after, the temperature that is preferably in more than 400 ℃ is annealed.When annealing in this way, in P type AlGaN, generally can obtain 1 * 10 17/ cm 3～1 * 10 19/ cm 3Carrier concentration.Yet, when making the LED device, can omit the 2nd P type cover layer 62 that forms by AlGaN.
P type contact layer 15 is formed by P type nitride-based semiconductor.If with binary or ternary mixed crystal such as GaN or AlGaN formation, can obtain the contact layer of excellent in crystallinity.If form P type contact layer with GaN especially, then can make it to reach good Ohmic contact with positive electrode material.As for the material that is used for positive electrode 17, preferably use to contain Ni and Au metal material.
According to the first embodiment of the present invention, a P type cover layer 61 that is formed by P type AlGaN is formed with active layer 14 contact, the 2nd P type cover layer 62 that is formed by its band gap P type AlGaN also wideer than the crack band of a P type cover layer 61 is formed with a P type cover layer 61 contact.With this structure, might realize that one has had photoconductive layer effect double as the one P type cover layer 61 of the protective layer of active layer 14 has been reached the 2nd P type cover layer 62 of limiting layer effect, the luminescent device of high emission output is arranged.
According to a second embodiment of the present invention, provide a kind of nitride partly to lead luminescent device, this device is identical with embodiment 1, accompanies an active layer between n type nitride semiconductor layer and P type nitride semiconductor layer.Said n type nitride semiconductor layer comprises that (talking about from the active layer side) has a n type cover layer that is formed by n type nitride-based semiconductor that contains indium and gallium or n type GaN and the 2nd n type cover layer that is formed by its band gap n type nitride-based semiconductor also wideer than the tectal band gap of a n type.The tectal thickness of the one n type is 10
Figure C20051012671200161
In the scope of～1.0 μ m.
Fig. 2 shows the profile of illustrative according to the structure (LD knot) of the luminescent device of second embodiment of the invention.With reference to Fig. 2, luminescent device comprises a substrate 21, presses the stacked n type contact layer 22 of described order, the 2nd n type cover layer 72, a n type cover layer 71, active layer 23, P type cover layer 24 and P type contact layer 25 on substrate.Form a current-limiting layer 26 on the surface of P type contact layer 25, this layer formed by the insulating material that opening 26a is arranged.On the surface of this current-limiting layer 26, form the positive electrode 27 that links to each other with P type contact layer 25 by opening 25a.On the other hand, connect in the n type and form a negative electrode 28 on the surface of ergosphere 22.In a LED device, then do not form current-limiting layer 26.
Characteristic and the explanation in first embodiment substrate 11, n type contact layer 12, active layer 13 and P type contact layer 15 described can be applicable to substrate 21, n type contact layer 22, active layer 23 and P type contact layer 25 respectively.
In the second embodiment of the present invention, the 2nd n type cover layer 72 should be by its band gap n type nitride-based semiconductor also wideer than the band gap of a n type cover layer 71, and best n type nitride-based semiconductor by binary or ternary mixed crystal is as being made of GaN or AlGaN.In these materials, that best is the n type AlGaN of ternary mixed crystal, because if the 2nd P type cover layer is made of this n type AlGaN, can make difference in band gap and refractive index difference in band gap and the refractive index greater than an active layer 23 and a n type cover layer 71.Though to the restriction of the tectal thickness of the 2nd n type without any harshness, for the n type AlGaN layer of the high-crystal quality that obtains to have not a particle of crackle, its thickness can be preferably 500
Figure C20051012671200162
～the scope of 1 μ m in.Yet, in the manufacturing of LED device, can save the 2nd n type cover layer 72 that forms by AlGaN, n type contact layer 22 has replaced the 2nd n type cover layer naturally.
A n type cover layer 71 that contacts with active layer 23 is by the n type nitride-based semiconductor that contains In and Ga, or n type GaN formation.The thickness of the one n type cover layer 71 should be preferably 10
Figure C20051012671200171
To the scope of 1 μ m, preferably be selected in 30
Figure C20051012671200172
In～0.1 mu m range.When the thickness that makes a n type cover layer 71 greater than 10
Figure C20051012671200173
The time, can make the first n type cover layer 71 play the effect of resilient coating between active layer 23 and the 2nd n type cover layer 72.That is, a n type cover layer 71 that is formed by lnGaN or GaN is original the softest in nature, thereby can absorb the strain of coefficient of thermal expansion differences initiation between the 2nd n type covering 72 that formed by lattice constant mismatch and AlGaN and the active layer 23.Because a n type covers 71 existence,, active layer 23, the 2nd n type cover layer 72 and P type cover layer 24 are cracked even the thickness of active layer 23 is thin again.In other words, because a n type cover layer 71 plays a part resilient coating, even its thickness is not more than 100 Active layer is elastically deformable also, has therefore reduced the crystal defect of active layer.Because a kind of like this effect, although active layer approach, active layer still can keep its good crystal mass, thereby can increase emission output.In addition and since attenuate active layer, according to strained quantum well effect or excitation-emission effect, also can increase luminous output.If adopt the material of n type GaN as a n type cover layer 71, can obtain poor a little this but almost with adopt the available same effect of InGaN.
In order to realize the LD device, the thickness of n type covering 71 should be preferably 100
Figure C20051012671200175
In the scope of～1.0 μ m, be 100 because work as its thickness
Figure C20051012671200176
Or when bigger, a P type cover layer 71 can play the effect of photoconductive layer.On the other hand, very thin if active layer becomes, as the situation in embodiment 1, adopt a n type cover layer 71 as the photoconductive layer that light is limited in the luminescent device of the present invention, then the restriction to the light in the active layer may become not exclusively.Luckily, owing to constitute a n type cover layer 71 as the effect that AlGaN or GaN play buffering in the case, make the attenuate of active layer become feasible.With the thickness adjusted of a n type cover layer 71 also is that it is important less than 1.0 μ m extremely.If the thickness of a n type cover layer 71 surpasses 1.0 μ m, the color meeting blackening of InGaN forms high-quality InGaN film and can become difficult.And, in final crystal, can form a large amount of holes, thus be difficult to make the LED or the LD device of high output, may be because the emission of device output be extremely low.
According to a second embodiment of the present invention, make to form with active layer 23 to contact, and the 2nd n type cover layer 72 that is formed by its band gap n type AlGaN also wideer than the band gap of a n type cover layer 71 is formed with a n type cover layer contact by n type InGaN or the formed n type cover layer 71 of n type GaN.According to this structure, situation at the LD device, a n type cover layer 71 that plays the photoconductive layer effect and the luminescent device that plays the 2nd n type cover layer 72 of light limiting layer effect might be realized having, under the situation of LED device, the luminescent device of high emission output might be realized.
A third embodiment in accordance with the invention provides a kind of nitride semiconductor photogenerator, and this device as embodiment 1, is provided with an active layer between n type nitride-based semiconductor and P type nitride semiconductor layer.Above-mentioned P type nitride semiconductor layer comprises: talk about the 2nd P type cover layer that has a P type cover layer that is formed by the P type nitride-based semiconductor that contains aluminium plus gallium and to be formed by its band gap P type nitride-based semiconductor also wideer than the tectal band gap of a P type from active layer.Above-mentioned n type nitride semiconductor layer comprises, talk about from active layer, a n type cover layer that is formed by the n type nitride-based semiconductor that contains indium and gallium and the 2nd n type cover layer that is formed by the also wide n type nitride-based semiconductor of the tectal band gap of its bandwidth ratio the one n type are arranged.
Fig. 3 schematically illustrates the profile according to the structure of the luminescent device of third embodiment of the invention (LD structure).With reference to Fig. 3, this luminescent device, comprise a substrate, press the stacked n type contact layer 32 of narrative order, the 2nd n type cover layer 82, a n cover layer 81, an active layer 33, a P type cover layer 91, the 2nd P type cover layer 92 and P type contact layer 34 at this substrate.On P type contact layer 34 surfaces, form the current-limiting layer 35 that forms by the insulating material that wherein is formed with opening 35a.On the surface of this current-limiting layer 35, form the positive electrode 36 that links to each other with P type contact layer 34 by opening 35a.On the other hand, on the surface of n type contact layer 32, form a negative electrode 37.
In the third embodiment of the present invention, the thickness of a P type cover layer 91 should be preferably 100
Figure C20051012671200181
In the scope of～1.0 μ mn, preferably be selected in 100
Figure C20051012671200182
In the scope of～0.5 μ m, the thickness of a n type cover layer 81 should preferably be controlled at 10 simultaneously
Figure C20051012671200183
The scope of～1.0 μ m preferably is controlled at 30
Figure C20051012671200184
The scope of～0.1 μ m.
The third embodiment of the present invention is being represented one of luminescent device optimum structure.When this structure was used for the LD device, a n type cover layer 81 played a part photoconductive layer; The 2nd n type cover layer 82 plays a part light limiting layer; The one P type cover layer 91 plays a part photoconductive layer; And the 2nd P type cover layer 92 plays a part light limiting layer.
Also be applicable to substrate 31, n type contact layer 32, the 2nd n type cover layer 82, a n cover layer 81, the active layer 33 of the 3rd embodiment with reference to described characteristics of first and second embodiment and explanation, the one p type cover layer 91, the two p type cover layers 92 and P type contact layer 34.For example, n type contact layer 32 should preferably be formed by n type GaN; The 2nd n type cover layer 82 is preferably formed by n type AlGaN; The one n type cover layer 81 is preferably formed by n type InGaN; Active layer 33 is preferably formed by the InGaN of non-doping; The one p type cover layer is preferably formed by p type AlGaN; The 2nd P type covers 92 and is preferably formed by P type AlGaN; And P type contact layer 34 is preferably formed by P type GaN.
A fourth embodiment in accordance with the invention provides a kind of nitride semiconductor photogenerator that is provided with as the active layer of embodiment 1 between n type nitride semiconductor layer and P type nitride semiconductor layer.Above-mentioned P type nitride semiconductor layer comprises: a P type cover layer that is formed by the P type nitride-based semiconductor that contains aluminium plus gallium, contact with active layer, its thickness is 10
Figure C20051012671200191
1.0 in the scope of μ m.
Though according to the expression in the accompanying drawings of structure of the luminescent device of the 4th embodiment, basically with shown in Figure 1 identical, that is substrate, n type and P type contact layer, active layer and n type and the tectal thickness of P type and material are basically with described identical with reference to figure.The main feature of the 4th embodiment is that the thickness of first cover layer 61 shown in Figure 1 is 10
Figure C20051012671200192
In the scope of～1.0 μ m.According to the 4th embodiment, can save n type contact layer 12 shown in Figure 1 or n type cover layer 13, also can save the 2nd P type cover layer 62 or P type contact layer 15, or save both simultaneously.
As mentioned above, the n type cover layer that contacts with active layer among the 4th embodiment is preferably by the n type nitride-based semiconductor that contains In and Ga InGaN particularly, or formed by n type GaN.Because the n type cover layer that is formed by InGaN plays a part a kind of resilient coating, absorb because the strain that coefficient of thermal expansion differences between cover layer and the active layer and lattice constant mismatch cause, thereby although the thickness of active layer is thin again, also can avoid in active layer, going out crackle, and keep its good crystal mass, increase emission output.In addition, because the attenuation of active layer, because strained quantum well effect or excitation-emission effect can increase luminous output.
The main feature of the fourth embodiment of the present invention is that the tectal thickness of a P type is located at 10
Figure C20051012671200201
In the scope of～1.0 μ m.When active layer is SQW or MQW structure, form and the P type cover layer of the contacted thickness of active layer below 1 μ m by P type AlGaN, also be very important.If a P type overburden cover greater than 1 μ m, may form crackle at a P type cover layer, make it to be not suitable for as luminescent device.Otherwise, if the tectal thickness of a P type is less than 10
Figure C20051012671200202
As mentioned above, active layer is decomposed probably, thereby has reduced luminous output.
Unexamined Japanese Patent Application Publication 6-21511 discloses a kind of luminescent device that structurally is similar to the luminescent device of the 4th embodiment.Yet this unexamined Japanese Patent Application Publication is different with the present invention on the tectal thickness of a P type.That is, open according to this, make the P type cover layer that constitutes by GaN or AlGaN grow into the thick of 2 μ m at active layer.Otherwise according to the present invention, P type cover layer is only formed by AlGaN, and its thickness is below 1 μ m.As reference embodiment 1 explain that compare with InAlGaN with other nitride-based semiconductor such as InGaN, InGaN, AlGaN can be transformed into the P type easilier, thereby in the middle of these nitride-based semiconductors, AlGaN can form the P type layer of high hole carrier concentration.So, when forming P type cover layer, can obtain the very luminescent device of high emission output with P type AlGaN.If make AlGaN be formed with the thick-layer of 2 μ m, this layer almost can not change the P type into, and the intrinsic character of AlGaN crystal can form crackle in resulting crystal in growing into thickness process like this simultaneously.So,, or be difficult to produce by the described luminescent device of above-mentioned unexamined Japanese Patent Application Publication or almost can not be luminous.By contrast, a fourth embodiment in accordance with the invention makes that the tectal kind of formed P type is that its thickness is definitely definite on thin active layer, so can produce the nitride semiconductor photogenerator with utility structure.
Fig. 4 is the curve chart of expression emission output with respect to the variation of the thickness of a P type cover layer 61 that is similar to luminescent device shown in Figure 1.Specifically, Fig. 4 illustrates the relative emission output of a LED device, and this device comprises: thickness is that n type contact layer (GaN) 12, the thickness of 4 μ m is 500
Figure C20051012671200211
N type cover layer (InGaN) 13, thickness be 20
Figure C20051012671200212
The active layer of (single quantum) (InGaN) 14, thickness respectively are that the P type cover layer (AlGaN) 61 of 0.1 μ m and the 2nd P type cover layer (AlGaN) 62 and thickness are the P type contact layer (GaN) 15 of 0.1 μ m.That is electrode 17 is directly to be formed on the P type contact layer 15.
By the figure finding, when the thickness of a P type layer 61 surpassed 1 μ m, emission output was tending towards rapid decline.This can be interpreted into the crystallinity deterioration that has formed crackle and make device on a p type cover layer 61.As can be seen from figure 4, tectal thick the making of a p type should be selected in 10 under the situation of LED
Figure C20051012671200213
(0.001 μ m) is to 1 μ m).Yet with regard to LD device situation shown in the first and the 3rd embodiment, the tectal thickness of a P type should be preferably 100
Figure C20051012671200214
More than, if because the tectal thickness of a P type changes to 100
Figure C20051012671200215
More than, it just can not play the effect of photoconductive layer.
Fig. 5 illustrates the change curve of emission output with respect to the thickness of a n type cover layer 71 that is similar to luminescent device shown in Figure 2.Specifically, shown in Figure 5 is-the relative emission output of LED device, and this device comprises: thickness is that n type contact layer (GaN) 22, the thickness of 4 μ m is that n type cover layer (AlGaN) 72, the thickness of 0.1 μ m is 20
Figure C20051012671200216
A n type cover layer (InGaN) 72, thickness be 20
Figure C20051012671200217
The active layer of (single quantum) (InGaN) 23, thickness are P type cover layer (AlGaN) 24 of 0.1 μ m and the P type contact layer (GaN) that thickness is 1 μ m.
As by Fig. 5 finding, when the thickness of a n type cover layer 71 surpassed 1 μ m, emission output was tending towards rapid decline.This crystallinity that can be interpreted into device degenerates, as the crystal deepening or produce pit in crystal.On the contrary, if the thickness less than 30 of a n type cover layer 71
Figure C20051012671200218
The emission output of luminescent device is tending towards descending.This preferred thickness that shows a n type coating 71 is 30
Figure C20051012671200219
More than, a n type cover layer 71 that is formed by InGaN by this condition can play the effect of resilient coating effectively.Simultaneously, if the thickness of a n type cover layer 71 is thinner than 10
Figure C200510126712002110
It does not a bit have the effect of resilient coating so, because there is a large amount of crackles to produce in active layer 23 and cover layer 72 and 24, thereby makes it be difficult to make device, has reduced emission output simultaneously widely.So the thickness of the n type cover layer 71 in the second embodiment of the invention should be preferably 10
Figure C20051012671200221
The scope of～1 μ m, preferably be selected in 30
Figure C20051012671200222
In the scope of～0.1 μ m.
Fig. 6 and 7 show respectively according to active layer of the present invention be the relative emission output of luminescent device of quantum well structure and trap layer thickness or and barrier layer thickness between relation.As shown in these figures, the thickness of trap layer should be 70 Below, preferably be selected in 50 Below, and the thickness of barrier layer should be 150
Figure C20051012671200225
Below, preferably be selected in 100
Figure C20051012671200226
Below.
A kind of nitride semiconductor light-emitting device according to fifth embodiment of the invention comprises that its feature class is similar to active layer the foregoing description 1 and that first first type surface and second surface are arranged; A n type cover layer that is formed by the n type nitride-based semiconductor that contains indium and gallium forms with first first type surface of active layer and contacts.
A kind of nitride semiconductor photogenerator according to sixth embodiment of the invention comprises that its property class is similar to above-mentioned first embodiment and has first first type surface and the active layer of second first type surface; A P type cover layer that is formed by the P type nitride-based semiconductor that contains indium and gallium forms with second first type surface of active layer and contacts.
Fig. 9 represents the profile of the luminescent device structure of illustrative the 5th embodiment; Figure 10 represents the profile of illustrative according to the luminescent device structure of this 6th embodiment.Explain the of the present invention the 5th and the 6th embodiment below in conjunction with accompanying drawing.
Luminescent device shown in Figure 9, comprise a substrate 121, stacked successively one resilient coating 122, that is used to relax the lattice mismatch between substrate 121 and the nitride-based semiconductor n type contact layer 123, the 2nd n type cover layer 124, a n type cover layer 125, active layer 126, the 2nd P type cover layer 128 and that are used for forming negative electrode thereon is used for forming the P type contact layer 129 of positive electrode thereon thereon.
Luminescent device shown in Figure 10, comprise a substrate 131, stacked successively one resilient coating 132, that is used to relax the lattice mismatch between substrate 131 and the nitride-based semiconductor contact layer 133, the 2nd n type cover layer 134, active layer 136, a P type cover layer 137, the 2nd P type cover layer 138 and that are used for forming the n type of negative electrode thereon is used for forming the P type contact layer 139 of positive electrode thereon thereon.
In the 5th and the 6th embodiment, active layer 126 and 136 can be the single quantum that the content by its indium can form according to the InGaN of required band gap variation.Another program, active layer 126 and 136 can be a lamination, this lamination is by the different separately laminated film of component, as being made of InGaN/GaN or InGaN/InGaN (its component is different with the former), thereby forms multi-quantum pit structure.Active layer can be the single quantum well of n type or P type and any one structure in the Multiple Quantum Well.Yet when the active layer of quantum well structure is a non-doped layer, what can obtain narrow half-band width can be with-can be with energy level emission between emission, excitation-emission or quantum well, realizes that at this moment LED device and Laser Devices are desirable.Another program, active layer 126 and 136 can mix with donor impurity and/or acceptor impurity.If can control to the identical quality of crystallinity with the active layer of non-doping to the crystallinity of the active layer that is mixed with impurity, then can compare with non-doping active layer by mixing with donor impurity, further improve can be with-can be with luminous intensity.Also can be by mixing with acceptor impurity, can make peak wavelength from the peak wavelength that can be with-can be with emission amplitude, but in the case, half-band width will be broadened to the about 0.5eV of low energy side shifting.If active layer is mixed simultaneously with acceptor impurity and donor impurity, compare with the active layer of only mixing with acceptor impurity, can further strengthen the luminous intensity of active layer.If what desire formed is the active layer of mixing with acceptor impurity, preferably should make the conduction type of active layer be transformed into the n type by mixing with donor impurity such as Si with the doping acceptor impurity.Yet because active layer is launched the desirable high light that should launch by of the present invention can be with-can being with, the InGaN that adopts non-doping is as the optimal material of active layer.Say alternatively,, compare that the crystallinity of the layer of gained degenerates probably with non-doping active layer if active layer is mixed with impurity.Yet, adopt the InGaN of non-doping to make the luminescent device of active layer, reducing V f(forward voltage) value aspect is better than being mixed with the luminescent device of impurity.The thickness of each trap layer and barrier layer can be with 1 value of being explained be identical in conjunction with the embodiments in the active layer of quantum well structure.
Have structure shown in Figure 9 luminescent device with active layer 126 contacted n type cover layers 125 preferably by a n type In xGa 1-xN (0＜X＜1) constitutes.The x value can be controlled at the preferable range of 0＜x≤0.5, be more preferably 0＜x≤0.3, be preferably in the scope of 0＜x≤0.2.The carrier concentration of the one n type cover layer 125 preferably should be 1 * 10 18/ cm 3～1 * 10 20/ cm 3Generally, along with the increase of the mol ratio of In in InGaN, make the crystallinity of compound be tending towards worsening.So in order to obtain the practical InGaN layer that presents high emission output, preferably making the x value is In below 0.5 xGa 1-xN.If carrier concentration is lower than 1 * 10 18/ cm 3, can reduce the electronics injection ratio of charge carrier to the InGaN active layer, this can reduce luminous output.On the contrary, if carrier concentration surpasses 1 * 10 20/ cm 3, then the tectal crystallinity of a n type can degenerate, so can reduce luminous output.
Have (the 6th embodiment) shown in Figure 10 structure luminescent device with active layer 136 contacted P type cover layers 137 preferably by P type In yGa 1-yN (0≤y＜1) constitutes.The y value can be controlled at the preferable range of 0≤y＜0.5, better in 0≤y＜0.3, is preferably in the scope of 0≤y＜0.2.The carrier concentration of the one P type cover layer 137 should preferably be controlled at 1 * 10 17/ cm 3～1 * 10 19/ cm 3Scope in.The y value is limited in is not higher than 0.5 reason and the x value is limited in not to be higher than 0.5 reason identical.If carrier concentration is lower than 1 * 10 17/ cm 3, charge carrier is to the hole injection efficiency meeting step-down of InGaN active layer, so reduced luminous output.Otherwise carrier concentration is if be higher than 1 * 10 19/ cm 3, the crystallinity that a P type covers can degenerate, thereby can reduce luminous output.
In the nitride semiconductor photogenerator of routine, its active layer mainly is made of InGaN, is arranged at mainly between a pair of cover layer that is made of AlGaN, when the reduced thickness of active layer, cracks probably in InGaN active layer and AlGaN cover layer.For example, be the reduced thickness to 200 of active layer When following, in active layer and cover layer, form a large amount of crackles inevitably, thereby be difficult to make it to make luminescent device.Obviously, because cover layer is very hard, can not flexibly relax the lattice mismatch and the coefficient of thermal expansion differences at the interface between active layer and the AlGaN cover layer on physical property by this thin InGaN active layer.Because the slight crack in cover layer and active layer can not make the active layer attenuate.
Simultaneously, by the present invention the 5th and the 6th embodiment, form a n-type cover layer 125 and a p-type cover layer 137 that all comprises In and Ga again, every layer contacts with 136 with the active layer 126 that comprises In and Ga respectively, as shown in Figures 9 and 10.These n-type cover layers 125 and a p-type cover layer 137 are set play resilient coating effect between active layer and the 2nd n-type cover layer 124 or the resilient coating effect between active layer and the 2nd p-type cover layer 138 respectively.Promptly, because containing first cover layer 125 and 137 its crystallization properties of In and Ga comes down to soft, thereby, first cover layer 125 and 137 can absorb any stress that produces owing to lattice constant mismatch, and since contain Al and Ga second cover layer 124 and 138 with active layer 126 and 136 between any stress of causing of different thermal coefficient of expansion.And, even active layer thickness is done thinly, can not cause the active layer 126 and 136 and second cover layer 124 and 138 to break yet.Since the stress absorption effect of first cover layer 125 and 137, even active layer is done very thinly, active layer energy strain, thereby make its crystal defect reduce to minimum, thus realize single quantum well or many quantum well structures.And, even active layer is done thinly, also can keep the degree of crystallinity of active layer admirably, make it might improve emission output.And, because the active layer thinning might cause quantum effect and priming effect.Thereby improve the luminous output of luminescent device.Luminescent device routinely.Require active layer thickness to make more than 1000 dusts, break to prevent to produce in cover layer and the active layer.Yet because thermal coefficient of expansion difference and lattice constant mismatch, active layer always is added with stress.And because the active layer thickness of conventional luminescent device has surpassed the critical thickness that allows active layer above-mentioned strain to occur, thereby conventional active layer can not be a strain.Therefore, cause crystal defects a large amount of in the active layer, and make it enough emissions of energy level can not occur to energy level.
Afterwards, with the influence of the gross thickness of the gross thickness of explanation the one n-type cover layer 125 and active layer 126 and an active layer 136 and a p-type cover layer 137.Require the gross thickness of a n-type cover layer 125 and active layer 126 and the gross thickness of an active layer 136 and a p-type cover layer 137 will be controlled at more than 300 dusts.In other words, the first tectal gross thickness that contains the active layer of In and Ga and contain In and Ga preferably is controlled at more than 300 dusts.Because, if the thickness of nitride semiconductor layer (active layer+first cover layer) that contains In and Ga might form crackle less than 300 dusts in active layer and in first and second cover layers.Cause the reason of this crackle to be considered to, because the stress that lattice constant mismatch or above-mentioned different heat expansion coefficient cause is on the interface between the 2nd n-type cover layer 124 that contains Al and Ga and the active layer 126, or act on the 2nd p-type cover layer 138 and the interface between the active layer 136 that contains Al and Ga.And when second cover layer that contains Al and Ga and contain In and the active layer of Ga between when first cover layer of resilient coating effect has been set, can alleviate this stress, suppress active layer and neutralize and crack in first and second cover layers.And from alleviating the viewpoint of these stress, the brilliant nitride-based semiconductor that forms of soft junction that contains In and Ga preferably should grow into the above thickness of 300 dusts.For example, in the 5th embodiment, when a n-type cover layer 125 formed thickness and is not less than a few dust, even when the thickness of active layer 126 is 3000 dusts, also difficult formation broken in active layer and cover layer.In other words, a n-type cover layer 125 can thick 300 dusts, and active layer 126 can be that several dusts are thick.Yet in the 5th embodiment, if the thickness of a n-type cover layer 125 is bigger, a n-type cover layer 125 preferably will form big thickness, and therefore, active layer can make thinner easily.
Among the present invention the 5th embodiment, require the 2nd n-type cover layer 124 to use n-type Al aGA 1-aN (0≤a＜1) constitutes." a " value can be controlled in the scope of 0≤a≤0.6.Be preferably in the scope of 0≤a≤0.4.Because the crystallization of AlGaN is difficult, therefore, a 〉=0.6 can increase the possibility that cracks among the AlGaN itself suddenly.Carrier concentration in the 2nd n-type cover layer 124 requires to be controlled at 5 * 10 17/ cm 3To 1 * 10 19/ cm 3In the scope, if carrier concentration is less than 5 * 10 17/ cm 3, the resistivity of AlGaN can increase, because cause the Vf of luminescent device higher.Thereby may reduce luminous efficiency.The thickness of second cover layer 124 can be at 50 dusts in the scope of 1.0 μ m.
Among the present invention the 6th embodiment, require with p-type Al bGa 1-bN (0≤b＜1) constitutes the 2nd p-type cover layer." b " value can be controlled in the scope of 0≤b≤0.6, and preferably in the scope of 0≤b≤0.4, the reason of restriction " b " value scope is identical with relevant the 2nd n-type cover layer 104 described reasons.The carrier concentration of the 2nd p-type cover layer 138 requires to be controlled to be 1 * 17cm -3, the positive hole of the charge carrier injection efficiency that enters active layer can reduce, and therefore, reduces luminous output.On the other hand, if carrier concentration is higher than 1 * 10 19Cm -3, the degree of crystallinity of AlGaN degenerates, and therefore might reduce luminous output.The thickness of this second cover layer 138 can formation 50
Figure C20051012671200261
In 1.0 mu m ranges.Owing to use the nitride semiconductor layer that contains Al and Ga to constitute the 2nd n-type cover layer 134 and the 2nd p-type cover layer 138, thereby, its skew of being with respect to active layer 136, the one p-type cover layers 135 and a p-type cover layer 137 can strengthen, to increase luminous efficiency.
By the present invention the 5th embodiment, can constitute and a n type cover layer 125 or the n-type contact layer 123 that contact with the 2nd n type cover layer 124 with n-type GaN formation.This n-type GaN is suitable for obtaining the ohmic contact with negative electrode the best, thereby has reduced the Vf of luminescent device.And, because its degree of crystallinity is better than the degree of crystallinity of the nitride-based semiconductor of other ternary or quaternary crystal, thereby can improve a n-type cover layer 125 and the tectal degree of crystallinity of the 2nd n-type of on this n-type GaN, growing, therefore improved the output of made luminescent device.With n-type contact layer 125 electrode material of excellent ohmic contact being arranged for example is the metallization material that contains It and Al, it also can be alloy, or it is laminated, for example be the laminated of Ti layer and Al layer, when this material is can realize good Ohmic contact during with the illuvium Ti deposit and that n-type GaN contacts, the carrier concentration that requires this n-type contact layer 123 is 5 * 10 17To 5 * 10 19Cm -3In the scope.If carrier concentration is less than 5 * 10 17Cm -3, be difficult to constitute ohmic contact with electrode.Therefore, may make the Vf of luminescent device higher.On the other hand, carrier concentration is higher than 5 * 10 19Cm -3, the degree of crystallinity of n-type GaN and other nitride semiconductor layer can degenerate, and might reduce luminous efficiency.
By the present invention the 6th embodiment, can constitute and a p-type cover layer 137 or the p-type contact layer 139 that constitutes by p-type GaN that contacts with the 2nd p-type cover layer 138.This p-type GaN is suitable for obtaining the ohmic contact better with positive electrode, and therefore, the Vf of luminescent device reduces.The electrode material that can constitute excellent ohmic contact with p-type contact layer 139 for example is the metallization material that contains Ni and Au.When this material is during with Ni illuvium deposit and that p-type GaN contacts, can realize fabulous ohmic contact.Require the carrier concentration controlization 1 * 10 of this p-type contact layer 139 17To 1 * 10 19Cm -3Scope in.If carrier concentration is less than 1 * 10 17Cm -3, be difficult to form ohmic contact with electrode.On the other hand, when carrier concentration greater than 1 * 10 19Cm -3The time, the degree of crystallinity of p-type GaN itself degenerates, and therefore may reduce luminous efficiency.
Nitride semiconductor photogenerator by the present invention the 7th embodiment comprises an active layer, and its feature is identical with above-mentioned first embodiment, and one first first type surface and one second first type surface are arranged.Form the n-type cover layer that the usefulness that contacts with first first type surface of active layer does not contain the n-type nitride-based semiconductor formation of aluminium.The 2nd p-type cover layer of the p-type nitride-based semiconductor formation that contains Al and Ga that contacts with second first type surface of active layer is set.
Figure 11 is the crosscut schematic diagram of the luminescent device structure of the present invention the 7th embodiment.Luminescent device shown in Figure 11, comprise a substrate 151, resilient coating 152 is arranged on it, be used to alleviate the lattice mismatch between substrate 151 and the nitride-based semiconductor, be formed for constituting n-type contact layer 153, the two n-type cover layers 154 of negative electrode on the resilient coating 152, the one n-type cover layer 155, active layer 156, the two p-type cover layers 158 and the p-type contact layer 159 that is used to constitute positive electrode, these layers are put by described order choosing.
Among the 7th embodiment, a n-type cover layer 155 that forms on first first type surface of active layer 156 does not require it is the n-type nitride-based semiconductor that contains In and Ga as among the 5th embodiment, but can be the n-type nitride-based semiconductor that does not contain aluminium.That is, in the specific embodiments of the present invention the 5th and the 6th embodiment combination, available GaN makes a n-type cover layer 155.More particularly, a n type cover layer 155 will be used n-type In xGa 1-xN (0≤x＜1) constitutes.The scope of " x " can be more preferably 0≤x≤0.3 in 0≤x≤0.5, and best scope is 0≤x≤0.2.The carrier concentration of the one n-type cover layer 155 requires to be controlled at 1 * 10 18Cm -3To 1 * 10 20Cm -3In the scope, because, if constitute the first tectal In xGa 1-x" x " value among the N is chosen in below 0.5, can obtain to have in the practicality luminescent layer of high emission output.If carrier concentration is less than 1 * 10 18Cm -3, the electron injection efficiency that enters the InGaN active layer can reduce, and therefore, reduces luminous output.On the other hand, if carrier concentration is higher than 1 * 10 20Cm -3, the tectal degree of crystallinity of a n-type degenerates.Therefore, may reduce luminous output.
Form the 2nd p-type cover layer 158 (being to be placed on above the p-type cover layer 157) that contacts with second first type surface of active layer 156 in Figure 11 with the p-type nitride-based semiconductor that contains Al and Ga.More particularly.Require with p-type Al bGa 1-bN (0≤b≤1) constitutes the 2nd p-type cover layer 158." b " value can be controlled in the scope of 0≤b≤0.6.When " b " value is controlled at 0.6 when following, can obtain flawless AlGaN crystal, thereby, improved its degree of crystallinity.Therefore, luminous output can improve.Require the carrier concentration of the 2nd p-type cover layer 158 to be controlled at 1 * 10 17Cm -3To 1 * 10 19Cm -3In the scope.If carrier concentration is less than 1 * 10 17Cm -3, the positive hole injection efficiency that enters the charge carrier of active layer can reduce, and therefore luminous output reduces.On the other hand, if carrier concentration is higher than 1 * 10 19Cm -3, the degree of crystallinity of AlGaN degenerates, and therefore may reduce luminous output.The thickness of this second cover layer 138 can be formed in 50 dust to 1.0 micrometer ranges.Constitute the 2nd p-type cover layer 158 with the nitride semiconductor layer that contains Al and Ga, its skew of being with respect to active layer 156 can increase, thereby has improved luminous efficiency.
The feature of active layer 156 can be with the first, the 5 described identical with the 6th embodiment.
By the present invention the 7th embodiment, a p-type cover layer 157 that constitutes with the p-type nitride-based semiconductor that does not contain aluminium can be arranged between active layer 156 and the 2nd p-type cover layer 158, as shown in figure 11.More particularly, require with p-type In gGa 1-gN (0≤g＜1) constitutes a p-type cover layer 157." y " value can be in 0≤y≤0.5, and better scope is 0≤y≤0.3, is preferably 0≤y≤0.2.Also can adopt the GaN that resilient coating is had no adverse effect to make the material of a p-type cover layer 157.Require the carrier concentration of a p-type cover layer 157 to be controlled at 1 * 10 17Cm -3To 1 * 10 19Cm -3In the scope.The reason of limiting carrier concentration is identical with the described reason of a p-type cover layer.
Require the gross thickness of a n-type cover layer 155 and active layer 156, or the gross thickness of active layer 156, the one n-type cover layers 155 and a p-type cover layer 157 to be controlled at more than 300 dusts preferably.The reason that limits gross thickness by this mode is same as described above, and even gross thickness is more than 300 dusts, can alleviate the stress on cover layer and the active layer, splits to avoid line occurring in cover layer and the active layer.
By the present invention the 7th embodiment, the 2nd n-type cover layer 154 that the usefulness that contacts with a n-type cover layer 155 contains the n-type nitride-based semiconductor formation of Al and Ga can be set.Require with n-type Al aGA 1-aN (0≤a＜1) constitutes the 2nd n-type cover layer 154." a " value can be controlled in the scope of 0≤a≤0.6, is preferably in the scope of 0≤a≤0.4.Because, if " a " is controlled at and is not more than 0.6 and can be suppressed at the possibility that cracks among the AlGaN itself.The carrier concentration of the 2nd n-type cover layer 154 requires to be controlled at 5 * 10 17Cm -3To 1 * 10 19Cm -3In the scope.If carrier concentration is less than 5 * 10 17Cm -3, the electron injection efficiency that enters active layer 156 can reduce, and therefore reduces luminous output.On the other hand, if carrier concentration is higher than 1 * 10 19Cm -3, the degree of crystallinity of AlGaN degenerates.Therefore might reduce luminous output.The thickness of second cover layer 154 can be in 50 dust to 1.0 micrometer ranges.Constitute into the 2nd n-type cover layer 154 with the nitride-based semiconductor that contains Al and Ga, its skew of being with respect to an active layer 156 and a n-type cover layer 155 can increase, and therefore increases luminous delivery efficiency.
By the present invention the 7th embodiment, can be provided with and a n-type cover layer 155 or the n-type contact layer 153 that constitutes with n-type GaN that contacts with the 2nd n-type cover layer 154, and the p-type contact layer 159 of using p-type GaN formation that contact with the 2nd p-type cover layer 158 is set simultaneously.The carrier concentration of this n-type contact layer 153 requires to be controlled at 5 * 10 17Cm -3To 5 * 10 19Cm -3Scope in.On the other hand, the carrier concentration of p-type contact layer 159 requires to be controlled at 1 * 10 17Cm -3To 1 * 10 19Cm -3In the scope, it is same as described above to select GaN to make the reason of contact layer material, simultaneously, under the situation of n-type contact layer 153, has improved the degree of crystallinity of the nitride-based semiconductor of growth on it especially, and its reason is same as described above.The carrier concentration of n-type contact layer 153 requires to be controlled at 5 * 10 17Cm -3To 5 * 10 19Cm -3In the scope.The carrier concentration of p-type contact layer 159 requires to be controlled at 1 * 10 17Cm -3To 1 * 10 19Cm -3In the scope.
By the present invention the 7th embodiment, first multilayer film 100 that at least two kinds of different nitride-based semiconductors of component constitute also can be set on the outside of a n-type cover layer 155, and/or second multilayer film 200 that at least two kinds of different nitride-based semiconductors of component constitute is set on the outside of the 2nd p-type cover layer 158, as reflective membrane.
Figure 12 is the cutaway view with luminescent device of this reflective membrane.Figure 13 is the perspective view of luminescent device shown in Figure 12.These illustrate the structure of Laser Devices.100 is first multilayer films among the figure, and 200 is second multilayer films.First multilayer film 100 constitutes with second multilayer film, 200 each nitride-based semiconductor different with index of refraction with different component, and first multilayer film 100 and second multilayer film 200 are alternately stacked.Under the condition of for example λ/4n (λ-wavelength, n-refractive index), constitute two-layer above structure, with the emission wavelength of reflection active layer 156.As shown in figure 12, first multilayer film 100 is arranged between the 2nd n-type cover layer 154 and the n-type contact layer 153.Second multilayer film 200 is arranged between the 2nd p-type cover layer 158 and the p-type contact layer 159, therefore, if laser generation is to being used as for example strip electrode below 10 microns, positive electrode as shown in Figure 13, when working, can be limited in the active layer by the light of these multilayer films, produce vibration easily to make it with active layer 156 emissions.The conduction type of these multilayer films is determined by mixing with donor impurity or acceptor impurity.Among the embodiment shown in Figure 12, first multilayer film 100 is formed between the 2nd n-type cover layer 154 and the n-type contact layer 153.Yet first multilayer film 100 also can form in n-type contact layer 153.Also can in p-type contact layer 159, form second multilayer film 200.Even in these contact layers, form these multilayer films, the light emission effect of restricted too active layer 156.Also can save any film in first multilayer film 100 and second multilayer film 200.For example, saved first multilayer film 100, can on the surface of sapphire substrate 151, form reflective membrane and replace first multilayer film 100.
As shown in figure 12, if use insulating material, make substrate as sapphire, prepare Laser Devices, made Laser Devices structure can be an a kind of flip-over type system, that is, the positive and negative electrode in this system is all from stretching out with the limit.In this case, as shown in figure 12, should be arranged at first multilayer film 100 that n-type layer forms on one side the contact layer 153 that constitutes negative electrode horizontal plane p-type layer on one side on.Because, if first multilayer film 100 be arranged on contact layer 153 horizontal plane substrate 151 on one side on.The difference of the refractive index between the 2nd n-type cover layer 154 and the n-type contact layer 153 has become little, therefore, the light of active layer 156 emission can enter in the n-type contact layer 153 that is arranged on below the active layer 156, and this is the peculiar function of using such as the dielectric substrate of sapphire of nitride semi-conductor laser.
Constituting at least a in two kinds of nitride-based semiconductors of multilayer film should be made of the nitride-based semiconductor that contains In and Ga, as by In cGa 1-cN (0≤x＜1) or GaN constitute.Because, GaN layer or In cGa 1-cThe N layer is playing the resilient coating effect with a plurality of individual layers when repeatedly putting formation one multilayer film with a plurality of individual layers.Therefore, can effectively avoid in other individual layer, cracking.Above-mentioned effect is attributable to these GaN and In cGa 1-cThe crystalline texture of N layer is more soft than the crystalline texture of AlGaN layer.On the contrary, constituting gross thickness with multilayer Al GaN layer is multilayer film more than 0.5 micron.The Al content difference of every film.Crackle will inevitably occur in the multilayer film, make it be difficult to make required device.
The most preferred embodiment that constitutes two kinds of nitride-based semiconductor combinations of multilayer film is that wherein a skim is with GaN or In cGa 1-cN makes, and another tunic is with containing Al and or the nitride-based semiconductor of Ga, for example Al dGa 1-dN (0≤d＜1) makes.Because In cGa 1-cThe refractive index of N and Al dGa 1-dThe refractive index of N has very big difference, makes full use of these materials, and presses emission wavelength, can design the multilayer film with big reflectivity.And, because In cGa 1-cN plays the resilient coating effect, can constitute flawless Al dGa 1-dTherefore the N layer can be realized the multilayer film of structure more than 10 layers.In this way, InN, the refractive index of each is respectively 2.9,2.5 and 2.15 among GaN and the AlN.The refractive index of supposing mixed crystal meets Vegard ' s law, then can calculate the refractive index of these mixed crystals by component ratio.
By the nitride semiconductor photogenerator of the present invention the 8th embodiment, comprising: an active layer, it has one first first type surface and one second first type surface, and is made of the nitride-based semiconductor that contains In and Ga.The feature of the 8th embodiment is, a n-type cover layer that constitutes with the band gap n-type nitride-based semiconductor that contains In and Ga bigger than active layer band gap contacts with the first master meter surface layer of active layer, simultaneously, with the band gap Ga type p-type nitride-based semiconductor that contain In bigger, for example p-type In than the band gap of active layer zGa 1-zThe p type cover layer that N (0≤z＜1) constitutes contacts with second first type surface of active layer.And, by the 8th embodiment with the following basis that is found to be, and, if at In xGa 1-xOn first first type surface of N active layer or on second first type surface band gap is set and compares In xGa 1-xThe InGaN cover layer that the band gap of N layer is wide can improve the output of the luminescent device of making.
Figure 14 is the cross-sectional view by the structure of the luminescent device of the present invention the 8th embodiment.Luminescent device shown in Figure 14, comprise substrate 211, resilient coating 212 is arranged on it, be used to alleviate the lattice mismatch between substrate 211 and the nitride semiconductor layer, be formed with n-type contact layer 213 on it, be used to constitute negative electrode, the 2nd n-type cover layer 214, the one n-type cover layers 215, active layer 216, the p-type contact layer 219 of the one p-type cover layer 217, the two p-type cover layers 218 and formation positive electrode, stacked in this order these layers.
Active layer 216 (In xGa 1-xN) can be the n-type, also can be the p-type, but can be with emission and narrow emission wavelength partly to lead the angle consideration of the Laser Devices of width from obtaining to have strong bringing to, and active layer should be non-doped layer (undoping).And active layer 216 can be used n-type impurity and/or p-type doping impurity, if active layer 216 can be used n-type doping impurity, compares with the active layer that undopes, and can further improve to bring to the luminous intensity that can be with.By with p type doping impurity, might make peak wavelength can be with the peak wavelength of launching towards low-lying level limit drift 0.5ev bringing to.If active layer with n-type and two kinds of doping impurity of p-type, is compared with the active layer that only mixes with acceptor impurity, the luminous intensity of active layer can further strengthen.If active layer will be used p-type doping impurity, the different electric type the most handy n-type impurity of active layer such as Si mix with p-type impurity and are transformed into the n-type.For the active layer that excellent degree of crystallinity is arranged by growth obtains Laser Devices, wish most to prepare active layer, as the aforementioned with undoped material.Active layer is Multiple Quantum Well or single quantum well preferably.In this case, trap layer thickness and barrier layer thickness are as described in first embodiment.
The one n-type cover layer 215 (one deck n-type In only is set yGa 1-yN) or only the one p-type cover layer 217 (one deck p-type In is set zGa 1-zN) may be all enough, but it is two-layer preferably to constitute cover layer 215 and 217, as shown in figure 14.Because the crystal of a n type cover layer 215 and a p type cover layer 217 all contains In, is soft, these cover layers play the resilient coating effect as lining.So, can prevent that at the 2nd n type cover layer 214, the two p type cover layers 218 n-type contact layer 213 contacts with the p-type in any one deck in 219 and crackle occurs, this can illustrate below.As the thickness range of the InGaN of resilient coating preferably more than 300 dusts, in the combined overall thickness of an active layer 216 and a p type cover layer 215; In active layer 216 and a p type cover layer 217 combined overall thickness; Or in the combined overall thickness of active layer 216, the one n-type cover layers 215 and a p type cover layer 217.In the luminescent device structure, can save a n type cover layer 215, allow the 2nd n-type cover layer 214 to work, replace a n-type cover layer 215, or save a p type cover layer 218, allow the 2nd p type cover layer 218 to work, replace a p type cover layer 217, this illustrates below.
More than in the explanation, the n type cover layer 215, active layer 216 and the p type cover layer 217 that constitute with InGaN have been explained.Require the ratio of In among these InGaN of control in these layers, for example the value of " x ", " y ", " z " is below 0.5, to be more preferably below 0.3.Preferably below 0.2.Because the degree of crystallinity that increases these InGaN with the In mol ratio is tending towards worsening.Thereby, can reduce luminous output.Know molecular formula In xGa 1-xN, In gGa 1-gN and In zGa 1-zAlso comprise the Al that replaces a small amount of Ga in these components among the N, for example InAlGaN; With regard to these substitute, can not weaken the effect of these InGaN compositions in fact.For example, if molecular formula In A 'Al B 'Ga 1-a '-b 'B ' value among the N is not more than 0.1, the one n type cover layer, and active layer and the tectal primary action of the 2nd p type can not change.Yet,, can make the crystal hardening of generation owing to comprise Al.For maximum emission output is arranged, only with the InGaN ternary mixed crystal that does not contain aluminium, and, constitute a n type cover layer 215 without the quaternary mixed crystal of nitride-based semiconductor, an active layer 216 and a p type cover layer 217 are desirable.The n type nitride-based semiconductor that only contains Al and Ga is set, as n-type Al aGA 1-aThe 2nd n-type cover layer 214 that N (0≤a＜1) constitutes, or only contain the p type nitride-based semiconductor of Al and Ga, as p-type Al bGa 1- bThe 2nd p-type cover layer 218 that N (0≤b＜1) constitutes may be enough.But require to be provided with the 2nd n-type cover layer 214 that contacts with a n-type cover layer 215, require to be provided with the 2nd p type cover layer 218 that contacts with a p type cover layer 217 simultaneously, as shown in figure 14.The 2nd n type cover layer 214 and the 2nd p type cover layer 218 thickness separately should be in the scopes of 50 dusts to 0.5 micron.The ratio of Al in the AlGaN composition, promptly " a " or " b " value is below 0.6, is more preferably below 0.4.Because the AlGaN crystal is hard.If " a " or " b " value surpasses 0.6, crackle can occur, even the resilient coating that InGaN constitutes is set, also crackle can occur, and occur crackle probably if " a " or " b " value surpasses 0.6.
Should be understood that Al aGa -aAnd Al bGa 1-bThe Ga of trace can resemble the effect that this substitute of InAlGaN does not weaken those AlGaN compositions in fact with replacements such as In in the such expression formula of N.For example, IF expression In A 'Al bGa 1-a-b 'The value of a ' among the N is not more than 0.1, and the original effect of AlGaN does not change so.Yet, even because a spot of In can cause that also band gap narrows down, thus must take measures to make band gap greater than a n type cover layer 215, the band gap of active layer 216 and the 2nd P type cover layer 218.In addition, In also can cause the deterioration of final crystal structure, thereby causes the reduction of emission effciency.Therefore, be preferably in when forming the 2nd n type cover layer 214 and the 2nd P type cover layer 218 only with the such ternary mixed crystal of AlGaN that does not contain In, and without the polynary mixed crystal of nitride-based semiconductor.Because the 2nd n type cover layer 214 and the 2nd P type cover layer 218 be for containing the Al layer, so that its band gap with respect to a n type cover layer 215, active layer 216 and a P type cover layer 217 broaden.
The active layer and the first tectal preferred compositions are that those are by In yGa 1-yThe n type cover layer that N constitutes is by In xGa 1-xThe active layer that N constitutes and by In zGa 1-zThe P type that N constitutes is tectal, it should be noted, relational expression y＜x and z＜x must satisfy the viewpoint of band gap relation.Active layer preferably is made of Multiple Quantum Well or single quantum well, and preferably n type or non-doping.The active layer of a quantum well structure can based on can be with-can be with the light that sends narrow half-band width.
The best active layer and the first tectal combination are that those are by In yGa 1-yN constitutes a n type cover layer, by In xGa 1-xThe active layer that N constitutes and by In zGa 1-zThe P type cover layer that N constitutes and by Al bGa 1-bThe active layer that N constitutes.Because adopted these combinations, the nitride-based semiconductor double heterojunction that just makes formation have fine degree of crystallinity constitutes possibility, thereby can improve emission output greatly.
As shown in figure 14, n type contact layer 213 preferably contacts with the 2nd n type cover layer 214, and simultaneously, P type contact layer 219 contacts with the 2nd P type cover layer 218.Can form n type contact layer 213 and make it both to contact, contact with a n type contact layer 215 again with the 2nd n type covering 214.Equally, form P type contact layer 219, both can contact, can contact with a P type cover layer 217 again with the 2nd P type cover layer 218.In other words, if the 2nd n type cover layer 214 omits, n type contact layer 213 can contact with a n type cover layer 215, and same, if the 2nd P type cover layer 218 is omitted, P type contact layer 219 can contact with a P type cover layer 217.Under certain conditions, a n type cover layer 215 and the 2nd n type cover layer 214 all can be omitted, n type contact layer 213 will play cover layer like this.Equally, omit a P type cover layer 217 and the 2nd P type cover layer 218, P type contact layer 219 will play cover layer, yet,, be not omitted and compare with these layers if these cover layers are all omitted, emission effciency can greatly reduce, therefore, the structure of luminescent device as shown in figure 14 is an optimum structure of the present invention.
N type contact layer 213 and P type contact layer 219 preferably are made of the nitride-based semiconductor GaN that does not contain Al and In.Because these contact layers are suitable for forming electrode thereon, if these contact layers are to be made of the semiconductor with fine degree of crystallinity and high carrier concentration, contact layer can form good Ohmic contact with electrode material so.Therefore, using GaN is preferred plan.The preferred examples that can contact with n type contact layer 213 formation good ohmic is a metal material, comprising Ti and Al.Can also be metal material with the optimal selection of P type contact layer 219 formation good ohmic electrodes in contact materials, comprising Ni and Au.When a contact layer that is formed by GaN was used as the electrode bearing bed, the luminescent device with low Vf value and high-luminous-efficiency just can have been realized.
Figure 15 is the structure cross sectional representation of the luminous body of another example of the present invention.The perspective view of this device is the same with Figure 13.Luminous body shown in Figure 15 is a kind of luminescent device of having used multilayer film 100 and 200, and these multilayer films are the same with those films that illustrate with reference to Figure 12.
The nitride semiconductor photogenerator of the 9th embodiment according to the present invention provides a kind of its thermal coefficient of expansion n type cover layer that the N type nitride-based semiconductor littler than the thermal coefficient of expansion of active layer forms; The P type cover layer that the P type nitride-based semiconductor littler than the thermal coefficient of expansion of active layer constitutes with planting its thermal coefficient of expansion, with an active layer that contains the nitride-based semiconductor formation of In at least, and this active layer is clipped in the middle of a n type cover layer and the P type cover layer.Active layer is made into previously described single quantum well or multi-quantum pit structure, so just can obtain an energy and become the lower light of the intrinsic band-gap energy of branch than active layer.That is, active layer is made into single quantum well or multi-quantum pit structure, and the tensile stress that edge is parallel to active layer and cover layer interface direction has produced, and so just may send an energy and become the lower light of the intrinsic band-gap energy of branch than active layer.
In other words, luminescent device according to the 9th embodiment of the present invention, the thermal coefficient of expansion that it is characterized in that active layer is higher than the tectal thermal coefficient of expansion of a n type, and the tectal formation of a P type is in order to produce the tensile stress that an edge is parallel to active layer and cover layer interface direction.In order flexibly this stress application to be arrived active layer, active layer is made into single quantum well or multi-quantum pit structure, and the active layer band-gap energy is less like this, and the while can make the emission wavelength of active layer shift to one side of long wave.In addition, the thickness of trap layer and barrier layer is made into and drops to critical level in the active layer, makes the good InGaN layer of the degree of crystallinity of can growing like this and can not consider to contain the In ratio relatively large.
In aGa 1-aThe intrinsic band-gap energy of N can be solved by following formula
Eg＝Eg 1×a+Eg 2×(1-a)-a×(1-a)
Here Eg 1Be the band-gap energy (1.96ev) of InN, Eg 2It is the band-gap energy (3.40ev) of GaN.In aGa 1-aThe intrinsic emission wavelength of N thus formula to solve be 1,240/Eg.
For the above-mentioned explanation of single quantum well and multi-quantum pit structure, should reaffirm that some active layer of single quantum is single trap layer.The active layer of multi-quantum pit structure is made up of a series of trap layers and barrier layer, wherein, the staggered stack of trap layer and barrier layer, and the outmost surface of this layer two-layer be the trap layer.
Figure 16 is the cross sectional representation of the 9th embodiment luminescent device of the present invention.Luminescent device shown in Figure 16 comprises substrate 311, and resilient coating 312, n type contact layer 313 are arranged on it.The 2nd n type cover layer 314, the one n type cover layers 315, active layer 316, a P type cover layer 317, the 2nd P type cover layer 318 and P type contact layer 319, these layers are stacked on the substrate 311 by top described order.
In the 9th embodiment, active layer 316 is made of the nitride-based semiconductor that contains In, and grown one-tenth single quantum well or multi-quantum pit structure.Because it is softer relatively to contain the active layer 316 of In, and its thermal coefficient of expansion and other nitride-based semiconductor such as AlGaN or GaN compare higherly, so can change emission wavelength by the thickness attenuation that makes the trap layer, as has only a single quantum.The active layer 316 of quantum well structure can be that the n type also can be the P type.Consider in order to obtain the good emission light of colorimetric purity should make that active layer 316 preferably is made of non-doped layer by being with-can being with the semibelt width of launching the light wave that produces narrow.If the trap layer of active layer 316 is by In zGa 1-zN (0＜z＜1) forms, and active layer has relative cover layer the very thermal coefficient of expansion of big difference is arranged, and can realize having wave-length coverage by the light of ultraviolet to ruddiness by being with-can being with to send so.On the other hand, under the multi-quantum pit structure situation, barrier layer is not InGaN, but GaN.
Concerning a n type cover layer 315 suitable selections be compare with active layer have less thermal coefficient of expansion and band-gap energy higher, but n type In preferably xGa 1-xN (0≤x＜1).Because it is soft crystal that a n type cover layer 315 that is made of InGaN or GaN is compared with the nitride-based semiconductor that contains Al, so such n type cover layer has played the effect of resilient coating.Also we can say,,, will no longer have crackle so and be introduced into active layer 316 if active layer 316 constitutes quantum well structure because a n type cover layer 315 has played the effect of resilient coating.In addition, the effect of a this n type cover layer 315 the 2nd n type cover layer 314 and the 2nd P type cover layer 318 that can prevent to be created on respectively on first cover layer 315 and 316 cracks.
The 317 suitable selections of the one P type cover layer are to compare with active layer 316 to have higher band-gap energy and less thermal coefficient of expansion, but P type Al preferably yGa 1-yN (0≤Y＜1).Contain the Al nitride-based semiconductor such as P type AlGaN is used to constitute cover layer when one, and be connected when touching with the active layer with Multiple Quantum Well or single quantum, the emission effciency of resulting devices can improve.
Arbitrary layer can be omitted in the one a n type cover layer 315 and the P type cover layer 317.If a n type cover layer 315 is omitted, the 2nd n type cover layer 314 just will replace a n type cover layer 315.If a P type cover layer 317 is omitted, the 2nd P type cover layer 318 just will replace a P type cover layer 317.Yet being joined with active layer by the n type cover layer 315 that n type InGaN or n type GaN constitute is preferably.
According to the 9th embodiment of the present invention, the 2nd n type cover layer 314 and the n type cover layer 315 that are made of n type nitride-based semiconductor join, and this 2nd n type cover layer 314 is preferably by n type Al aGa 1-aN (0≤a≤1) constitutes.If a n type cover layer 315 is made of InGaN, just the 2nd n type cover layer 314 can be made of GaN or AlGaN.Because one to contain its thermal coefficient of expansion of nitride-based semiconductor of Al little and be hard crystal, when it is used to constitute the 2nd n type cover layer 314 and is connected with a n type cover layer 315, additional tensile stress can exert an influence to active layer, like this, the emission wavelength of active layer can be shifted to the long one side of wavelength.Link to each other with the first type surface of active layer 314 if contain the 2nd n type cover layer 314 of Al, the relative one side of the first type surface of active layer 316 should formerly form a P type cover layer 317 that is made of InGaN or GaN and serve as resilient coating so.
The 2nd n type cover layer 314 (Al aGA 1-aThe thickness of N (0≤a＜1) is preferably 50 In～1 mu m range.If the thickness of the 2nd n type cover layer 314 is controlled in this scope, a suitable tensile stress will put on active layer so.The value of " a " is 0.6 or less than 0.6 better, preferably 0.4 or less than 0.4.Even because the possibility that forms crackle in the 2nd n type cover layer 314 is owing to a n type cover layer 315 of growing becomes minimum, but the AlGaN crystal is still very hard, if the value of " a " still can crack at the AlGaN layer above 0.6 like this.Usually, the ratio of Al is high more in the AlGaN layer, and the active layer emission wavelength is just long more.
According to this embodiment, the 2nd p type cover layer 318 that is made of a p type nitride-based semiconductor links to each other with a p type cover layer 317.The 2nd p type cover layer 318 is preferably by p type Al bGa 1-bN (0≤b≤1) constitutes.If a n type cover layer 315 is made of AlGaN, then the 2nd p type cover layer 318 should be made of GaN and serves as contact layer.Link to each other with a first type surface of active layer 316 if contain the 2nd p type cover layer 318 of Al, then the opposite face of the first type surface of active layer (the n layer on one side) should formerly form a n type cover layer 315 that is made of InGaN or GaN and make resilient coating.
The effect of the 2nd p type cover layer 318 is identical with the 2nd n type cover layer 314, and the thickness of such the 2nd p type cover layer 318 is preferably also 50
Figure C20051012671200392
Between～1 μ m.The value of " b " is 0.6 or less than 0.6, is preferably 0.4 or less than 0.4.Usually, high more in the ratio of AlGaN layer Al, the active layer emission wavelength is long more.
Because adopted the nitride semiconductor layer that contains Al, perhaps GaN is as the 2nd n type cover layer 314 or as the 2nd p type cover layer 318, containing the n type of Al or the band-gap energy of p type cover layer 315 and 317 has so all increased than active layer 316, has therefore improved emission effciency.The thermal coefficient of expansion that increase is compared with active layer 316 poor is one side the active layer emission wavelength will be to long moving.
Next discuss and form active layer and tectal best of breed.The composition of at first suitable active layer 316 and first cover layer 315 and 317 is, as a n type cover layer by In xGa 1-xN (0≤x＜1) constitutes; Active layer is by In zGa 1-zThe quantum well structure of N (0≤z＜1) constitutes; The one p type cover layer is by In yGa 1-yN (0＜y＜1) constitutes.Certainly to consider band-gap energy in these combinations, so should satisfy the condition of x＜z.
When active layer 316 was single quantum, the thickness of trap layer should be 100
Figure C20051012671200401
Or 100
Figure C20051012671200402
Below; When active layer 316 was multi-quantum pit structure, the thickness of trap layer should be 100
Figure C20051012671200403
Or 100 Below, the thickness of barrier layer should be 150
Figure C20051012671200405
Or 150
Figure C20051012671200406
Below, so that obtain under the n type or the situation that undopes, directly being with-being with the light emission with narrow half-band width of emission.
The optimum combination of these layers is that the 2nd n type cover layer 314 is by Al aGA 1-aN (0≤a≤1) constitutes; The one n type cover layer 315 is by In xGa 1-xN (0≤x＜1) constitutes; Active layer 316 is by In zGa 1-zN (0＜z＜1) constitutes single quantum; The one p type cover layer 317 is by In yGa 1-yN (0≤y＜1) constitutes; The 2nd p type cover layer 318 is by Al bGa 1-bN (0≤b≤1) constitutes.In these compounds, any one in a n type cover layer 315 and the p type cover layer 317 or both can omit.When first cover layer omits, the 2nd n type cover layer 314 or the 2nd p type cover layer 318 will replace the first tectal position to play cover layer.If only by first cover layer 315,317 and the structure formed of active layer 316 be difficult to offer the enough tensile stresss of active layer, second cover layer that can contain Al in the growth of the outside of first cover layer 315 and 317 is used for increasing the poor of thermal coefficient of expansion between second cover layer 314,318 and the active layer 316.Therefore active layer is made a multi-quantum pit structure that constitutes by thin trap layer and thin barrier layer, or made the single quantum of having only thin trap layer, can reduce the band gap of active layer, emission wavelength is moved to long wave by the tensile stress at interface.
Be that the n type cover layer in the device architecture and the gross thickness of active layer are controlled at 300 according to another embodiment of the invention
Figure C20051012671200407
Or more, a n type cover layer 3.5 is made of n type nitride-based semiconductor that contains In or n type GaN here.Because when this gross thickness is 300
Figure C20051012671200408
Or more for a long time, the effect that GaN or InGaN layer just serve as a resilient coating, this just allows active layer to be made of quantum well structure, and can prevent that a p type cover layer 317 and the 2nd p type cover layer 318 from cracking.
Should be clear, In here xGa 1-xN, In yGa 1-yN and In zGa 1-zThese expression formulas of N also comprise the situation that these a small amount of Ga in forming or In are substituted by Al, and this replacement can't weaken the effect of InGaN as InAlGaN.Equally, expression formula Al aGA 1-aN and Al bGa 1-bAlso comprise the situation that these a small amount of Al in forming or Ga are substituted by In among the N, also can not weaken the effect of AlGaN as this replacement of InAlGaN.
In addition, can mix alms giver or acceptor impurity of active layer 316.If the doping of active layer 316 does not influence its degree of crystallinity, so, compare with the active layer that undopes, the doping active layer will increase its can with-can be with the emission intensity.By the doping acceptor impurity,, peak wavelength can be moved 0.5ev from the peak wavelength that can be with-can be with emission to the low energy direction though half-band width will broaden.Alms giver and acceptor impurity if active layer mixes simultaneously, the emissive porwer of active layer will be stronger than only mixing acceptor impurity.If active layer doping acceptor impurity, the conductivity of active layer can transfer the n type to by mixing donor impurity such as Si and acceptor impurity simultaneously.Because therefore active layer should be able to preferably make active layer with this material of plain InGaN ideally by being with-can being with emission emission high light according to the present invention.In other words, if active layer mixes, its degree of crystallinity is gone bad manyly than undoping, and compares with the luminescent device that mixes, and the advantage of making the luminescent device of active layer with plain InGaN is lower Vf value.
Multi-quantum pit structure active layer among the present invention is made up of InGaN/GaN or InGaN/InGaN (different on the component), is promptly formed by the thin layers that comprises trap layer/barrier layer.When active layer was multi-quantum pit structure, the relative single quantum of its emission effciency made moderate progress.The LED of multi-quantum pit structure or LD device, the thickness of its trap layer should be controlled at a few dust to tens dusts, and the thickness of potential barrier layer also should be controlled at a few dust to tens dusts.These interlaminate stacks form multi-quantum pit structure.More suitable trap layer thickness is 100
Figure C20051012671200411
Or littler, 70
Figure C20051012671200412
Or littler then better, bed thickness scope above-mentioned also can be used for the active layer of single quantum.On the other hand, more suitable barrier layer thickness is 150
Figure C20051012671200413
Or littler, preferably 100 Or it is littler.When making multi-quantum pit structure, trap layer and barrier layer doping alms giver or acceptor impurity.When a series of thin layers superposeed by this way, some distortions of lattice can flexibly be sponged by active layer.
As shown in figure 16, the n type contact layer 313 that is formed by n type GaN that is used for carrying electrode thereon preferably contacts with a n type cover layer 315 or the 2nd n type cover layer 314.Equally, the p type contact layer 319 that is formed by p type GaN that is used for carrying electrode thereon preferably contacts with a p type cover layer 317 or the 2nd p type cover layer 318.Because the 2nd n type cover layer 314 and the 2nd p type cover layer 318 are to be made of GaN, so contact layer 313 and 319 can omit.In this case, second cover layer 314 and 318 promptly serves as contact layer.Needing these contact layers 313 is because when electrode contacts with first cover layer that is made of ternary or more polynary mixed crystal or second cover layer with 319 reason, is difficult to obtain gratifying ohmic contact.And when making the contact layer material, just can obtain good ohmic contact with GaN.Good electrode ohmic contact has been arranged, just can obtain the luminescent device of low Vf and high emission efficiency.
Figure 17 is the trap layer thickness of active layer of a single quantum and the emission peak wavelength graph of a relation of luminescent device.It is plain In that the solid line of Figure 17 acceptance of the bid " α " is represented the active layer of luminescent device 0.05Ga 0.95The result of N, it is plain In that the dotted line of mark " β " is represented the luminescent device active layer 0.3Ga 0.7The result of N.The structure of these two kinds of luminescent devices all is in order by one the 2nd n type cover layer, one the one n type cover layer, an active layer, one the one p type cover layer, one the 2nd double-heterostructure that p type cover layer is constituted.In these two devices, the 2nd n type cover layer is the thick n type Al that mixes Si of 0.1 μ m 0.3Ga 0.7N, a n type cover layer is 500
Figure C20051012671200421
Thick In 0.01Ga 0.99The N layer, a p type cover layer is 20
Figure C20051012671200422
The thick p type Al that mixes Mg 0.01Ga 0.99N layer, the 2nd p-type cover layer are the p type Al that 0.1 μ m mixes Mg 0.3Ga 0.7The N layer.Emission wavelength shown in Figure 17 changes and changes along with active layer thickness.
" α " representative by In 0.05Ga 0.95The active layer that N constitutes according to it intrinsic band-gap energy sent ultraviolet light near 380 μ m, but by attenuate active layer thickness, can become and send orchid light, so just emission wavelength has been moved on near 420nm.On the other hand, " β " representative by In 0.3Ga 0.7The active layer that N constitutes, according to it intrinsic band-gap energy sent blue green glow near 480nm.Also can make it to launch pure green glow by attenuate active layer thickness, its wavelength is near 520nm.Resemble top illustratedly, can emission wavelength be moved to long wave by the thickness that attenuate is clipped in the active layer between a n type cover layer and a p type cover layer.That is to say, general bigger active layer thickness, emission is near the light of its intrinsic band-gap energy.In the active layer of single quantum in the present invention, urine obtains light lower than the intrinsic band-gap energy of trap layer or that wavelength is longer can to make band gap change to by attenuate trap layer thickness.And because active layer is the layer that undopes, it has the more crystalline degree than doped layer, and higher luminous efficiency can be arranged.Therefore, can obtain the light of the narrow half-band width of fine color purity by being with-can being with emission.
As the In that adopts conventional thickness zGa 1-zWhen N made active layer, last active layer had very poor degree of crystallinity.For example, when the ratio of In when promptly " z " is 0.3 to 0.5, degree of crystallinity variation, correspondingly show as very low emission effciency.Yet when active layer is thin,, also can obtain good degree of crystallinity even the ratio of In is quite high.
So the THICKNESS CONTROL of trap layer is 100
Figure C20051012671200431
Or following better, preferably 70
Figure C20051012671200432
Or it is littler.In the characteristic according to a routine luminescent device of the present invention that Figure 17 provides, give tensile stress different of active layer along with second cover layer and first cover layer, emission wavelength is different to the scope that long wave moves.Equally, suitable active layer thickness range also changes to some extent with the change of component of these layers.
As everyone knows, the thermal coefficient of expansion of AlN is 4.2 * 10 -6/ k, the thermal coefficient of expansion of GaN be 5.59 * -6/ k.Because the InN of crystalline state does not also obtain fully, so the thermal coefficient of expansion of InN is not clear.The thermal coefficient of expansion of supposing InN is the highest in these nitride-based semiconductors, has following order: InN＞Gan＞AlN.About the growth temperature of these nitride, be generally 500 ℃ or higher with the growth of MBE method, be 900 ℃ or higher sometimes with MOVPE.For example, with the growth of MOVPE method, at 700 ℃ or higher temperature growing InGaN, and at 900 ℃ of growth AlGaN.Therefore, there is a pair of cover layer of less thermal coefficient of expansion at high temperature to form when having relative active layer, accompany simultaneously the higher active layer of thermal coefficient of expansion therebetween, then when the high temperature of its growth is reduced to room temperature, because active layer has relatively large thermal coefficient of expansion, it will be subjected to tectal pulling force, and active layer is subjected to tensile stress being parallel on active layer and the tectal interface direction like this.Just because of this, it is minimum that the band-gap energy of active layer reduces to, and causes that emission wavelength is elongated.By In 0.05Ga 0.95N or In 0.3Ga 0.7The thermal coefficient of expansion of the active layer that N constitutes than the first and second tectal big reasons is, In the active layer ratio in these cover layers greatly.Therefore the tensile stress that is parallel to active layer and tectal interface has taken place, and so just makes the band-gap energy of active layer diminish, and with common being with-can be with and launch ratio, its emission wavelength moves to long wave.Because this tensile stress increases with the thickness attenuation of active layer, so can obtain the light wave longer than general emission wavelength.
The optimal luminescent device of the 9th embodiment of the present invention, comprise a n type cover layer that constitutes by n type nitride-based semiconductor that contains In or n type GaN, one active layer that constitutes greater than the tectal nitride-based semiconductor of a n type by its thermal coefficient of expansion that contains In at least that links to each other with a n type cover layer, wherein active layer is single quantum well or multi-quantum pit structure, so that obtain the band-gap energy lower light more intrinsic than active layer itself.The one n type cover layer of luminescent device and the gross thickness of active layer are controlled at 300
Figure C20051012671200441
Or more mostly be best.Another optimal luminescent device of the 9th embodiment, comprise one by the single quantum well of the nitride system semiconductor one-tenth that contains In or the active layer of volume minor structure, one by containing Al's and compare the P type cover layer that the P type nitride-based semiconductor of higher thermal expansion coefficient constitutes with active layer, so that obtain to compare with the intrinsic band-gap energy of active layer itself more low-energy light.
According to the ninth embodiment of the present invention, make another n type cover layer 315 that joins with the active layer 316 that contains In and Ga, the one n type cover layer 315 plays a part active layer and contains resilient coating between the 2nd n type cover layer 314 of Al, promptly since constitute a n type cover layer 315 contain InGaN or the intrinsic crystallinity of nitride-based semiconductor is soft, therefore since lattice constant mismatch or since between the 2nd n type cover layer 314 and the active layer 316 any distortion that difference produced of thermal coefficient of expansion all absorb by a n type cover layer 315.Owing to this reason, the possibility that imagination cracks at active layer 316 and the 2nd n type cover layer 314 had both made to be done active layer to such an extent that very thinly also can reduce.Because distortion can absorb by an aforesaid n type cover layer 315, so be 200 dusts or more hour, active layer can flexibly be out of shape by tension stress, so has reduced band-gap energy, and perhaps can widen emission wavelength at active layer thickness.In addition, the crystal defect of active layer can be reduced, and therefore, even do active layer very thin, also can also improve the crystallinity of active layer, has increased emission output thus.In order to make a n type cover layer 315 play resilient coating, should be preferably with the gross thickness with the active layer 316 of soft crystal structure and a n type cover layer 315 be controlled to be 300 dusts or more than.
If a p type cover layer is become by the nitride system semiconductor that contains Al, will improve emission output, this the chances are due to the fact that, the AlGaN easier p of the becoming type of comparing with other nitride-based semiconductor, or the decomposition of the active layer of being made by InGaN can stop by AlGaN in growth the one p type cover layer step process, yet its concrete reason is not clear.
The manufacturing of the luminescent device of being made up of nitride-based semiconductor can be used for example MOVPE (metal-organic chemical vapour deposition), and MBE (molecular beam epitaxy) or HDVPE (hydride vapor-phase epitaxy) method are finished.For example, luminescent device can be by the In of stack n type or p type on a substrate aAl bGa 1-a-bN (0≤a; 0≤b; A+b≤1) makes, so that obtain double-heterostructure.Material for as substrate can use sapphire (it comprises the C plane, R plane and A plane), SiC (comprising 6H-SiC and 4H-SiC), Si, ZnO, GaAs, spinelle (MgAl 2O 4, its (111) plane particularly), and monocrystalline oxide (as NGO).N type nitride-based semiconductor can obtain with non-dopant states, but also can be in its crystal growing process by with donor impurity such as Si, Ge or S are diffused in the semiconductor and obtain.P type nitride-based semiconductor can by in its crystal growing process with acceptor impurity such as Mg, Zn, Cd, Ca, Be or C are diffused in the semiconductor and make, or by the diffusion acceptor impurity and anneal under 400 ℃ of temperature then and make.
The present invention is described with reference to its 1st to the 9th embodiment, will further be explained by means of example below.Yet it should be as limitation of the present invention, with reference to the described feature of an embodiment with explain and can be applicable among other embodiment under the suitable situation.For example, can be applied to other embodiment, both make the material of each layer different with reference to illustrated each layer carrier concentration of the 5th and the 6th embodiment.
Example 1
This example 1 is described as follows with reference to Fig. 1.
At first, use TMG (trimethyl gallium) and NH 3As raw material, the resilient coating that growth is made by GaN under 500 ℃ of temperature on the C plane that is put in the Sapphire Substrate 11 in the reactor in advance, its thickness is 200 dusts.
Then, temperature is raised to 1050 ℃, in this case, silane gas is added to TMG and NH 3In, the n type contact layer 12 of growing thus and being made up of Si doped n type GaN, its thickness are that 4 μ m are thick.
Then, reduce the temperature to 800 ℃, and TMI (trimethyl indium) is added in the unstripped gas, grow thus by Si Doped n-type In 0.05Ga 0.95The n type cover layer 13 that N makes, its thickness is 500 dusts.
When keeping these 800 ℃ of temperature, growth is by non-Doped n-type In 0.2Ga 0.8It is thick that the active layer 14 of the single quantum that N forms reaches 20 dusts.
Then, temperature is raised to 1050 ℃ again, at this moment, uses TMG, TMA (trimethyl aluminium), NH 3And C P2Mg (cyclopentadienyl group magnesium) grows by Mg doped p type In 0.1Ga 0.9The p type cover layer 61 that N forms reaches 0.1 μ m thickness.
When this temperature of keeping 1050 ℃, growth is by Mg doped p type Al 0.3Ga 0.7The 2nd p type cover layer 62 that N forms reaches 0.5 μ m thickness.
Then, under 1050 ℃ temperature, the p type contact layer 15 that growth is made up of the Mg Doped GaN reaches 1.0 μ m thickness.
After reaction is finished, reduce the temperature to room temperature, and the gained wafer is taken out, under 700 ℃ of temperature, carry out wafer annealing then, so that reduce the resistivity of p type layer.Then, carry out etching, so that the surface of n type contact layer 12 is exposed from the superiors of p type contact layer 15.Finish be etched with after, on the surface of p type contact layer 15, make by SiO 2The current-limiting layer of forming and opening 16a is arranged 16 then, is made the positive pole of being made up of Ni and Au 17 on current-limiting layer 16, it is connected with p type contact layer 15 by opening 16a.Then, make the negative pole of forming by Ti and Al 18.
Then, Sapphire Substrate 11 surface finish of also not making nitride semiconductor layer are reached 90 μ m to reduce substrate thickness.Then, scribing and power break the M plane plane of hexagon prism side surface (in the hexagonal crystal system corresponding to) of Sapphire Substrate, to make laser chip.After intact, make dielectric multilayer film on the surface breaking of chip, and the gained chip is put on the fin, at room temperature this chip is carried out the laser generation test, in order to prove at 2.0KA/cm 2Under 450nm, produce laser generation under the threshold current density.
Example 2
This example 2 is described as follows with reference to Fig. 2.
With with example 1 in identical mode, on Sapphire Substrate 21, make GaN resilient coating, and adopt the MOVPE method to make the n type contact layer of forming by n type GaN 22 of 4 μ m thickness with 200 dust thickness.
Then, has 0.5 μ m thickness and by Si Doped n-type Al making 0.3Ga 0.7After made the 2nd n type cover layer 72 of N, make 500 dust thickness and mix the n type In of Si 0.05Ga 0.95The n type cover layer 71 that N forms.
Then, to have 20 dusts thick and by non-doping In in growth 0.2Ga 0.8The active layer 23 of the single quantum that N forms, intact after, it is thick and by Mg doped p type Al that deposit thereon sequentially has 0.5 a μ m 0.3Ga 0.7P type cover layer 24 that N forms and the p type contact layer 25 that has 1.0 μ m thickness and form by the Mg Doped GaN.
Then, adopt with example 1 in identical processing mode with the acquisition laser chip, it is put in carries out laser generation on the fin then, prove at 2.0KA/cm thus 2Under 450nm, produce laser generation under the threshold current density.
Example 3
This example 3 will be described as follows according to Fig. 3.
At first, adopt with example 1 in the identical method n type contact layer 32 on Sapphire Substrate 31, making GaN resilient coating and have 4 μ m thickness and form by n type GaN with 200 dust thickness by the MOVPE method.
Then, has 0.5 μ m thickness and by Si Doped n-type Al making 0.3Ga 0.7After the 2nd n type cover layer 82 that N makes, make and have 0.1 μ m thickness and by Si Doped n-type In 0.05Ga 0.95The n type cover layer 81 that N forms.
Then, growth has 20 dust thickness and by non-doping In 0.2Ga 0.8The active layer 33 of the single quantum that N forms, intact after, deposit thereon sequentially has 0.1 μ m thickness and by Mg doped p type Al 0.3Ga 0.7The p type cover layer 91 that N forms has 0.5 μ m thickness and by Mg doped p type Al 0.3Ga 0.7The 2nd p type cover layer 92 that N forms and the p type contact layer 34 that has 0.5 μ m thickness and form by Mg doped p type GaN.
Then, repeated with example 1 in after the identical treatment step, the gained laser chip is put on the fin to carry out laser generation, prove at 1.0KA/cm thus 2Threshold current density under under 450nm, produce laser generation, so can obtain to compare the LD device of threshold current density that will be low with first and second embodiment shown in the above-mentioned example.
Example 4
According to the step of example 3, just growth has the Si Doped n-type GaN layer of 0.1 μ m thickness to replace n type cover layer a 81 (Si Doped n-type In 0.05Ga 0.95N).
Then, deposit sequentially has the non-doping In of 30 dust thickness on cover layer 81 0.4Ga 0.6N trap layer and have the non-doping In of 50 dust thickness 0.08Ga 0.92The N barrier layer.Repeat these steps up to the multi-quantum pit structure that obtains to form and have 5 laminations of 190 dust gross thickness, constitute active layer 23 thus by trap layer+potential barrier layer+trap layer+potential barrier layer+trap layer.
Then, after forming active layer 23 according to example 3 in identical treatment step and obtain laser chip, it is put in after intact and carries out laser generation on the fin, prove at 0.9KA/cm thus 2Threshold current density under under 500nm, produce laser generation.
Example 5
By the step of example 1, just by Mg doped p type Al 0.1Ga 0.9First cover layer, 61 deposits that N forms reach after the 0.1 μ m thickness, and the p type contact layer 15 of 1.0 μ m degree is formed and had in growth by Mg doped p type GaN on first cover layer 61.
After reaction is finished, adopt with example 1 in identical method under 700 ℃ of temperature, carry out the annealing of wafer so that the resistivity of reduction p type layer.Then, carry out etching, so that the surface of n type contact layer 12 is exposed from the superiors of p type contact layer 15.Finish be etched with after, on the surface of p type contact layer 15, make the positive pole of forming by Ni and Au 17, then, make the negative pole of forming by Ti and Al 18, that is to say that difference is made dielectric multilayer film and then made the LED device.This LED shows at 200mAI f(forward current) issues blue-fluorescence under 45nm, and Vf (forward voltage) is 3.5V, and the emission of LED is output as 6MW, and it shows high output, and the semibelt width of emission spectrum is 20nm, and it shows sharp-pointed being with-can be with emission.
Example 6
According to the step of example 1, just omitted the formation of current-limiting layer 16 and dielectric multilayer film in the example 1, and anodal 17 by directly on p type contact layer 15, making described in the example 5, thus the LED device made.This LED device is at 20mA I fUnder show and turn blue look fluorescence under 450nm, and Vf is 3.5V.The emission of LED is output as 6mW, and it shows high output.Under the situation of example 5, the semibelt width of emission spectrum is 20nm, and it shows sharp-pointed being with-can be with emission.
Example 7
This example is corresponding to the fourth embodiment of the present invention, and will join Fig. 1 it is described as follows.
Adopt example 1 described same procedure, the n type contact layer 12 of on Sapphire Substrate 11, making GaN resilient coating and having 4 μ m thickness and form by n type GaN by the MOVPE method with 200 dust thickness.
Then, on the surface of n type contact layer 12, directly make and have 30 dust thickness and by non-doping In 0.2Ga 0.8The active layer 14 of the single quantum that N forms.After intact, deposit sequentially thereon has 0.05 μ m thickness and by Mg doped p type Al 0.1Ga 0.9The p type cover layer 61 that N forms and have the p type contact layer 15 that 0.5 μ m thickness Mg doped p type GaN forms.
Then, adopt with example 5 in identical method, on p type contact layer 15, directly make anodal 17, with acquisition LED device.This LED device is at 20mAI fUnder show and turn blue look fluorescence under 450nm, and Vf is 3.5V, the emission of LED is output as 7mW, it shows very high output.As the situation of example 5, the semibelt width of emission spectrum is 20nm, and it shows sharp-pointed being with-can be with emission.
Comparative example
According to the step of example 5, just in deposit Mg doped p type Al 0.1Ga 0.9The p type cover layer 61 that N forms reaches after the 2 μ m thickness, and the p type contact layer 15 that growth is made up of the Mg Doped GaN on first cover layer 61 reaches 1.0 μ m thickness.
After reaction is finished,, find wherein to be formed with a large amount of crackles with microscopic examination p type contact layer.In addition, similarly carry out wafer annealing, and similarly make the LED device by it.This LED device presents blue light-emitting, and wavelength is 450nm, and its Vf is at 20mA I fBe down the 10V height, the emission of LED is output as 100mW or following.
Example 8
This example 8 is described as follows with reference to Fig. 9.
At first, use TMG and NH 3As raw material, the resilient coating 122 that growth has 500 dust thickness and is made up of GaN under 500 ℃ of temperature on the C plane that is positioned over the Sapphire Substrate 121 in the reactor in advance.
Then, temperature is raised to 1050 ℃, in this case silane gas is removed TMG and NH 3Add beyond the adding, thus the n type contact layer 123 of growing and having 4 μ m thickness and forming by Si Doped n-type GaN.The carrier concentration of this n type contact layer 123 is 2 * 10 19/ cm 3
Then, under 1050 ℃ of uniform temps TMA is joined in the unstripped gas keeping, growth has 0.1 μ m thickness and by Si Doped n-type Al thus 0.3Ga 0.7The 2nd n type cover layer 124 that N is made.The carrier concentration of the 2nd n type cover layer 124 is 1 * 10 19/ cm 3
Then, reduce the temperature to 800 ℃, and by using TMG, TMI, NH 3With silane gas, growth has 500 dust thickness and by Si Doped n-type In 0.01Ga 0.99The n type cover layer 125 that N is made.The carrier concentration of the one n type cover layer 125 is 5 * 10 18/ cm 3
Keeping under 800 ℃ of these temperature, and by using TMG, TMI and NH 3, growth has 30 dust thickness and by non-doping In 0.05Ga 0.95The active layer 126 that N forms.
Then, temperature is raised to 1050 ℃ again, in this case, uses TMG, TMA, NH 3And Cp 2Grow 0.1 μ m thickness and be 1 * 10 of Mg by the hole of Mg doped p type cover layer 128 18/ cm 3
Under this temperature of 1050 ℃ of maintenances, by using TMG, NH 3And Cp 2Mg, the p type contact layer 129 that growth has 0.5 μ m thickness and is made up of Mg doped p type GaN.The hole of this p type contact layer 129 is 5 * 10 19/ cm 3
After reaction is finished, reduce the temperature to room temperature, and the gained wafer is taken out, under 700 ℃ of temperature, carry out wafer annealing then, so that reduce the resistivity of p type layer.Then, after making regulation pattern mask on uppermost p type contact layer 129 surfaces, carry out etching, so that the surface of n type contact layer 123 is exposed from uppermost p type contact layer 129.Finish be etched with after, on the surface of n type contact layer 123, make the negative pole of forming by Ti and Al, and on the surface of p type contact layer 129, make the positive pole of forming by Ni and Au.
After this mode of employing is made electrode, the gained wafer surface is cut into a plurality of chips, its each chip is that 350 μ m * 350 μ m are square, and is made into the LED device with 15 degree visual angles.This LED device is at 20mA I fPresenting peak wavelength down is the look fluorescence that turns blue of 415nm, and Vf is 3.5V, and the emission of LED is output as 6mw, and the semibelt width of emission spectrum is 20nm, and it presents the emission of high pure color.
Example 9
This example 9 is described as follows with reference to Figure 10.
According to the processing method identical and form doped with Al by n type Si with example 8 0.3Ga 0.7The 2nd n type cover layer 134 that N forms.Then, with example 8 under the same terms on the surface of second cover layer 134 growth have 40 dust thickness and by non-doping In 0.05Ga 0.95The active layer 136 that N forms.
Then, under 800 ℃ of temperature, pass through to use TMG, TMI, NH 3And Cp 2Mg and on active layer 136 deposit have 500 dust thickness and by Mg doped p type In 0.01Ga 0.99The p type cover layer 137 that N forms.
Then, after having formed first cover layer 137, according to example 8 in identical processing method and obtain LED device shown in Figure 10.This LED device presents peak wavelength under 20mA If be fluorescing of 410nm, and Vf is 3.5V, and the semibelt width of emission spectrum is 20nm, and the emission of LED is output as 5mW.
Example 10
This example 10 is described as follows with reference to Figure 11.
According to naming processing method identical in 8 up to forming by Si Doped n-type In 0.01Ga 0.99The n type cover layer 155 that N forms.Then, with example 8 similarity conditions under on first cover layer, 155 surfaces growth have 40 dust thickness and by non-doping In 0.05Ga 0.95The active layer 156 that N forms.
Then, under 800 ℃ of temperature, pass through to use TMG, TMI, NH 3And Cp 2Mg and on active layer 156 deposit have 500 dusts and by Mg doped p type In 0.01Ga 0.99The later hole of p type cover layer 157, the one p type cover layers, 157 annealing that N forms is 2 * 10 17/ cm 3
Example 11
Then, according to the processing method identical with example 8 to make by Mg doped p type Al 0.3Ga 0.7The 2nd p type cover layer 158 that N forms and the p type contact layer of forming by Mg doped p type GaN 159.After intact, according to obtaining the LED device shown in Figure 11 with example 8 same treatment methods.This LED device presents fluorescing of peak wavelength 420nm under 20mA And if Vf is 3.5V, and the semibelt width of emission spectrum is 20vm, and the emission of LED is output as 9mW.
According to the processing method identical with example 8 up to forming by Si Doped n-type Al 0.3Ga 0.7The 2nd n type cover layer 154 that N forms.
Then, the n type cover layer 155 that growth has 500 dust thickness and is made up of Si Doped n-type GaN on the 2nd n type cover layer 154.The electronic carrier concentration of the one n type cover layer 155 is 2 * 10 19/ cm 3
Then, adopt with example 10 in identical method deposit on a n type cover layer 155 have 40 dust thickness and by non-doping In 0.05Ga 0.95The active layer 156 that N forms.
Then, make by Mg doped p type Al according to the processing method identical with example 8 0.3Ga 0.7The 2nd p type cover layer 158 that N forms and the p type contact layer of forming by Mg doped p type GaN 159.After intact, obtain the LED device according to the processing method identical with example 8.This LED device presents the fluorescent emission of peak wavelength 415nm under 20mA If, and Vf is 3.5V, and the semibelt width of emission spectrum is 20nm, and the emission of LED is output as 5mW.
Example 12
According to the processing method identical with example 8, just active layer 126 consists of In 0.2Ga 0.8N obtains the LED device thus.This LED device presents the blue-fluorescence that peak wavelength is 455nm under 20mA If, and Vf is 3.5V, and the semibelt width of emission spectrum is 20nm, and the emission of LED is output as 5mw.
Example 13
Make the LED device that resembles example 8 according to same steps as, just active layer 126 is a multi-quantum pit structure, particularly, uses TMG under 800 ℃ of temperature, TMI and NH 3Growth has the non-doping In of 20 dust thickness 0.1Ga 0.9N trap film, growth has the In of 20 dust thickness then 0.02Ga 0.98The N barrier film.This processing procedure of triplicate, and last growth has the In of 20 dust thickness 0.1Ga 0.9N trap film is with the active layer 126 of the multi-quantum pit structure that obtains to have 140 dust gross thickness.So the LED device of preparation presents the blue-fluorescence of peak wavelength 420nm under 20mA If, and Vf is 3.5V, and the emission of LED is output as 7mv.
Example 14
According to preparing the LED device with example 8 same steps as, just DEZ (diethyl zinc) is used as acceptor impurity, silane gas as donor impurity, is had 50 dust thickness and uses Si and Zn doped n type In to make 0.05Ga 0.95The N layer.So the LED device that obtains presents the blue-fluorescence of peak wavelength 450nm under 20mA If, and Vf is 3.5V, and semibelt width is 70nm, and the emission of LED is output as 3mw.
Example 15
Adopt with example 8 in identical method, on n type contact layer 123, sequentially grow by Si Doped n-type In 0.01Ga 0.99The n type cover layer 125 that N forms is by non-doping In 0.05Ga 0.95The active layer 126 that N forms is by Mg doping P type Al 0.3Ga 0.7The 2nd P type cover layer 128 and P type contact layer 129 that N forms.Just, prepare LED, just do not make the 2nd n type cover layer 124 according to the step identical with example 8.The LED device of preparation like this presents peak wavelength 410nm under 20mA If fluorescence and Vf are 3.5V, and the emission of LED is output as 5mw.
Example 16
This example 16 is described as follows with reference to Figure 12 and 13.
According to step identical described in the example 8 up to forming n type contact layer 153.Then, reduce the temperature to 800 ℃, by using TMG, TMI, NH 3Grow with silane gas and to have 380 dust thickness by Si Doped n-type In 0.01Ga 0.99The film that N forms.Then, temperature is being raised to after 1050 ℃, by using TMG, TMA, NH 3Grow with silane gas and to have 390 dust thickness by Si Doped n-type Al 0.2Ga 0.8The film that N forms.These steps are repeated 20 times, the n type multilayer film 100 of growing thus, it is by ten layers of Si Doped n-type In 0.01Ga 0.99N and ten layers of Si Doped n-type Al 0.2Ga 0.8N is alternately laminated and form.
Then, adopt with example 10 in identical method deposit sequentially the 2nd n type cover layer 154, the one n type cover layers 155, active layer 156, the one P type cover layers 157 and the 2nd P type cover layer 158.
Then, reduce the temperature to 800 ℃, and by using TMG, TMI, NH 3And Cp 2Mg, growth has the Mg doping P type In of 380 dust thickness 0.01Ga 0.99The N layer.Then, temperature is raised to 1050 ℃ again, in this case, uses TMG, TMA, NH 3And Cp 2The Mg doping P type Al that Mg grows and has 390 dust thickness 0.2Ga 0.8The N layer.Repeat these steps, obtain the 2nd P type multilayer film 200 thus, it is by ten layers of Mg doping P type In 0.01Ga 0.99N and ten layers of Mg doping P type Al 0.2Ga 0.8N is alternately laminated and form.
After forming the 2nd P type multilayer film 200, same procedure growing P-type contact layer 159 on the surface of the 2nd P type multilayer film 200 in employing and the example 8 is with the preparation wafer.
Then, after same procedure is carried out being etched with of nitride semiconductor layer in employing and example 8, on the surface of uppermost P type contact layer 159, make regulation pattern mask, so that on n type contact layer 153, make the negative pole of width 50 μ m, and on P type contact layer 159, make the positive pole of width 10 μ m.When on n type contact layer 153, making a n type multilayer film 100, will automatically be arranged in order to the horizontal plane that bears negative pole lower than the level of a n type multilayer film 100, as shown in Figure 12.
Then, do not reach 90 μ m with making the Sapphire Substrate 151 of nitride semiconductor layer and the thickness that reduces substrate of surface finish on it.Be cut into chip fully then with the M plane scribing of Sapphire Substrate 151, and with prosperous of gained, its each chip is that 700 μ m * 700 μ m are square, and is made into the laser with strip geometry shown in Figure 13.Figure 13 has wherein constituted the photoresonance surface with the nitride semiconductor layer plane that the bar shape positive pole intersects vertically corresponding to according to this reality Laser Devices perspective view just.Remove electrode whole surface in addition with the covering of dielectric film (not shown).Then, the chip that so obtains is arranged on the fin, and with each electrode wire bond.When this chip is at room temperature stood laser generation, can prove at 1.5KA/cm 2Laser generation under 390nm under the threshold current density.
Example 17
This example 17 is described as follows with reference to Figure 16.
At first, use TMG and NH 3As raw material, the resilient coating 312 that growth has 500 dust thickness and is made up of GaN under 500 ℃ of temperature on the C plane that is arranged at the Sapphire Substrate 311 in the reactor in advance.
Then, temperature is raised to 1050 ℃, in this case silane gas is removed TMG and NH 3Add in addition, thus the n type contact layer 313 of growing and having 4 μ m thickness and forming by Si Doped n-type GaN.
Then, TMA is joined in the unstripped gas, keep 1050 ℃ uniform temp simultaneously, growth has 0.1 μ m thickness and by Si Doped n-type Al thus 0.3Ga 0.7The 2nd n type cover layer 314 that N is made.
Then, reduce the temperature to 800 ℃, and by using TMG, TMI, NH 3With silane gas, growth has 500 dust thickness and by Si Doped n-type In 0.01Ga 0.99The n type cover layer 315 that N is made.
Keeping under 800 ℃ of these temperature, by using TMG, TMI and NH 3, growth has 30 dust thickness and by non-doping In 0.8Ga 0.2The active layer 316 of the single quantum that N forms.
Then, remove TMG, TMI and NH by using 3Cp in addition 2Mg, growth has 500 dust thickness and by Mg doping P type In under 800 ℃ of temperature 0.01Ga 0.99The P type cover layer 317 that N forms.
Then, temperature is raised to 1050 ℃ again, in this case, uses TMG, TMA, NH 3And Cp 2Mg grows and has 0.1 μ m thickness and by Mg doping P type Al 0.3Ga 0.7The 2nd P type cover layer 318 that N forms.
Keeping under 1050 ℃ of these temperature, by using TMG, TMA, NH 3And Cp 2Mg, the P type contact layer 319 that growth has 0.5 μ m thickness and is made up of Mg doping P type GaN.
After reaction is finished, reduce the temperature to room temperature, and the gained wafer is taken out, under 700 ℃ of temperature, carry out wafer annealing then, so that reduce the resistivity of P type layer.Then, after making the mask of regulation pattern on the surface of uppermost P type contact layer 319, carry out etching, so that the surface of n type contact layer 313 is exposed from uppermost P type contact layer 319.Finish be etched with after, on the surface of n type contact layer 313, make by Ti and the made negative pole of Al, on the surface of P type contact layer 319, make by Ni and the made positive pole of Au then.
After this mode of employing is made electrode, the gained wafer is cut into chip, its each chip 350 μ m * 350 μ m are square, and are made into the LED device that tool 15 degree are looked courage.This LED device is at 20mA I fPresent the red fluorescence that peak wavelength is 650nm down.And Vf is 3.5, and the emission of LED is output as 0.7mw.
Example 18
Prepare LED according to the processing method identical with example 17, just active layer 316 has In in this example 0.05Ga 0.95The N composition also has 10 dust thickness.This LED device presents the bluish violet fluorescence of peak wavelength 425nm under 20wA If, the emission of LED is output as 5mw, and the semibelt width of emission spectrum is 20nm, and it shows the emission of high pure color.
Example 19
Prepare LED according to the step identical with example 17, just the composition of active layer 316 becomes non-doping In 0.2Ga 0.8N.This LED device presents the blue-fluorescence of peak wavelength 465nm under 20mA If, the emission of LED is output as 5mw, and the semibelt width of emission spectrum is 25nm, and it shows the blue-fluorescence emission of high color purity.
Example 20
Prepare the LED device according to the step identical with example 17, just growth has the Si Doped n-type In of 300 dust thickness 0.01Ga 0.99The N layer is as a n type cover layer 315, and growth has the non-Doped n-type In of 10 dust thickness 0.3Ga 0.7The N layer is as active layer, and growth has 300 dust thickness Mg doping In 0.01Ga 0.99The N layer is as a P type cover layer 317.This LED device presents the green fluorescence of peak wavelength 500nm under 20mA If, Vf is that 3.5V and semibelt width are 40nm, and the emission of LED is output as 4mw.
Example 21
In the program of example 17, after n type contact layer 313 formed, the active layer 316 of a single quantum directly was deposited on the n type contact layer 313, and this active layer 316 is by having 70 The In of thickness 0.4Ga 0.6The N layer constitutes.In this case, n type contact layer 313 is intended for a n type cover layer.Then, on active layer 316, form the 2nd P type cover layer 318, and form P type contact layer 319 thereon.With with example 17 in identical mode carry out subsequently process, obtain a LED device thus.This LED device presents green fluorescence, and peak wavelength is 525nm, and Vf is 3.5V, is under the 20mA condition at If, and half bandwidth is 40nm.The emission output of this device is 4mw.
Example 22
Except forming 300
Figure C20051012671200591
Thickness mix silicon n type GaN layer as a n type cover layer 315, form the non-doping In of 20a thickness then 0.3Ga 0.7Layer forms 300 again as active layer 316
Figure C20051012671200592
Thickness mix magnesium P type GaN layer as outside the P type cover layer 317, carry out as program identical in the example 167, prepare a LED device.The LED device of Huo Deing presents green light like this, and the peak value filter is long to be 515nm, and Vf is 3.5v, is under the 20mA condition at If, and half-band width is 40nm.The emission output of this device is 3mw.
Example 23
Except using DEZ as the acceptor impurity source, silane gas is used as the donor impurity source and has 50 with formation The In of thickness 0.05Ga 0.95N layer and mix as outside the active layer 316 with Si and Zn is carried out and is prepared LED as program identical in the example 17.The LED matrix of Huo Deing presents green fluorescence like this, and the peak value filter is long to be 480nm, and Vf is 3.5v, is under the 20mA condition at If, and half bandwidth is 80nm.The emission of this device is output as 2mw.
Example 24
In the program of example 17, form one and have 500
Figure C20051012671200594
Thickness mix silicon n type In 0.01Ga 0.99The N layer is as a n type cover layer 315.Then, in order to prepare active layer, form one and have 10
Figure C20051012671200595
The non-doping In of thickness 0.15Ga 0.85The N layer has 10 as quantum well layer (well louyer) and formation one
Figure C20051012671200596
The non-doping In of thickness 0.15Ga 0.85The N layer is as the barrier layer on this quantum well layer.Said process alternately repeats four times, forms one at last and has 10
Figure C20051012671200597
The non-doping In of thickness 0.15Ga 0.85The N quantum well layer has formed the active layer of a multi-quantum pit structure thus, and its gross thickness is 90
Figure C20051012671200598
Subsequently, form one and have 500
Figure C20051012671200599
The magnesium of thickness is mixed P type In 0.01Ga 0.99The N layer is as the P type cover layer on the active layer 316.Identical mode is carried out subsequent process in this example 17, obtains a wafer thus.
Subsequently, mode identical in this example 17 is carried out etching on nitride semiconductor layer, forms the mask of predetermined pattern on the P type contact layer that constitutes the superiors.After this, on this n type contact layer, form the mask of predetermined pattern.After this, on this n type contact layer 313, form the negative electrode of wide 20 μ m and on P type contact layer 319, form the positive electrode of wide 2 μ m.
Then, the surface of the Sapphire Substrate of inchoate nitride semiconductor layer on it is polished, make the thickness of this substrate reduce to 90 μ m.Subsequently, the M face of this Sapphire Substrate is by scribing, and synthetic wafer is cut into the square substrates that each is 700 μ m * 700 μ m, and is made into laser with strip geometry as shown in figure 13.Figure 13 shows the perspective view according to this routine laser aid, and the face of wherein vertical with the positive electrode of bar shaped tangent nitride semiconductor layer has constituted an optical resonance face.Then, the substrate of above-mentioned acquisition is set in the fin, and is each electrode welding lead.When this substrate bears laser generation, at 1.5KA/cm 2Threshold current intensity under, the laser generation of 390nm is proved.
Example 25
Except that active layer and the tectal formation of a P type, execution prepares a LD device as program identical in the example 24.In this example, in order to form active layer, forming a thickness is 25
Figure C20051012671200601
Non-doping In 0.15Ga 0.85N is as quantum well layer, and forming a thickness then is 50
Figure C20051012671200602
Non-doping In 0.05Ga 0.95N is as the barrier layer on the quantum well layer.This process is repeated 13 times, finally forms quantum well layer, has obtained to have 1000 thus
Figure C20051012671200603
The active layer of the multi-quantum pit structure of thickness.On this active layer 316, be formed with one and have 500 Thickness and by Al 0.05Ga 0.95The P type cover layer that N constitutes.The LD device of Huo Deing is at 1.0KA/cm like this 2Present the laser generation of 415nm under the threshold current intensity.
Example 25
Except that forming active layer, identical program prepares a LD device in the execution example 24.To form a thickness be 25 in order to form active layer in this example
Figure C20051012671200605
Non-doping In 0.15Ga 0.85N is as quantum well layer, and forming a thickness then is 50
Figure C20051012671200606
Non-doping In 0.05Ga 0.95N is as the barrier layer on the quantum well layer.This process repeats 26 times, finally forms this quantum well layer, has obtained to have 1,975 thus
Figure C20051012671200607
The active layer of the multiple quantum well layer of thickness.The LD device of Huo Deing is in room temperature like this, 4.0KA/cm 2Present the laser generation of 415nm under the threshold current intensity.
Example 27
The blue LED of the 450nm that obtains in example 7, the green LED of the 515nm that obtains in example 21, with an emission wavelength 660nm who constitutes by common GaSs stock or LlInGaP stock, the red LED of luminous output 3mw is assembled into an image point, and makes a LED display that is constituted by 16 * 16 (image points).Subsequently, a plurality of LED displays are set up and are prepared into the full-color LED display with 320 * 240 pixels.This display can the surface light of white light emission 10,000 nits.
As mentioned above, be possible according to the invention provides good LED device of luminous output and brightness and LD device.

Claims (14)

1. nitride semiconductor photogenerator is characterized in that comprising:
An active layer, this active layer is made of the nitride-based semiconductor that contains indium and gallium, and has first and second first type surfaces;
The one n type cover layer, it is made of the n type nitride-based semiconductor that does not contain aluminium, and setting contacts with described first first type surface of active layer; With
A p type cover layer, it is made of a p type layer and the 2nd p type layer, a described p type layer is made of the p type nitride-based semiconductor that does not contain aluminium and setting contacts with described second first type surface of active layer, and described the 2nd p type layer is made of the p type nitride-based semiconductor that contains aluminium plus gallium and is arranged on the described p type layer.
2. according to the device of claim 1, it is characterized in that a described p type layer is by p type In xGa 1-xN constitutes, wherein 0≤x＜1.
3. according to the device of claim 1, it is characterized in that described active layer is a quantum well structure, this structure comprises that thickness is
Figure C2005101267120002C1
Or trap layer still less.
4. according to the device of claim 1, it is characterized in that described active layer and the tectal gross thickness of a described n type are
Figure C2005101267120002C2
Or it is more.
5. according to the device of claim 1, it is characterized in that described active layer, the gross thickness of a described n type cover layer and the tectal described p type layer of described p type is
Figure C2005101267120002C3
Or it is more.
6. according to the device of claim 1, it is characterized in that further comprising one the 2nd n type cover layer, it is made of the n type nitride-based semiconductor that contains aluminium plus gallium, and setting contacts with a described n type cover layer.
7. according to the device of claim 1, it is characterized in that further comprising a n type contact layer that constitutes by n type GaN, and it is set contacts with a described n type cover layer.
8. according to the device of claim 6, it is characterized in that further comprising a n type contact layer that constitutes by n type GaN, and it is set contacts with described the 2nd n type cover layer.
9. according to the device of claim 1 or 2, it is characterized in that further comprising a p type contact layer that constitutes by p type GaN, and it is set contacts with described the 2nd p type layer.
10. according to the device of claim 1 or 2, it is characterized in that a described n type cover layer is by In xGa 1-xN constitutes, and wherein x is 0.5 or littler.
11. according to the device of claim 2, it is characterized in that described active layer has quantum well structure, this structure comprises that thickness is
Figure C2005101267120003C1
Or trap layer still less.
12., it is characterized in that described active layer and the tectal gross thickness of a described n type are according to the device of claim 2
Figure C2005101267120003C2
Or it is more.
13. according to the device of claim 2, it is characterized in that further comprising the 2nd n type cover layer, the 2nd n type cover layer is made of the n type nitride-based semiconductor that contains aluminium plus gallium, and is set to contact with a described n type cover layer.
14. according to the device of claim 13, it is characterized in that further comprising the n type contact layer that constitutes and be set to contact by n type GaN, and its feature is that also described the 2nd n type cover layer is by Al with described the 2nd n type cover layer yGa 1-yN constitutes, wherein 0＜y＜1.
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JP2020021798A (en) * 2018-07-31 2020-02-06 日機装株式会社 Nitride semiconductor light-emitting element and manufacturing method thereof
CN109390443B (en) * 2018-12-04 2024-02-09 西安赛富乐斯半导体科技有限公司 Semi-polar gallium nitride single quantum well layer light-emitting device and manufacturing method thereof
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