CN1856915A - Nitride semiconductor device and method for manufacturing same - Google Patents

Abstract

Disclosed is a nitride semiconductor device comprising a p-type nitride semiconductor layer, an n-type nitride semiconductor layer, and an active layer interposed between the p-type nitride semiconductor layer and the n-type nitride semiconductor layer. The p-type nitride semiconductor layer has a first p-type nitride semiconductor layer containing Al and Mg, and a second p-type nitride semiconductor layer containing Mg. The first p-type nitride semiconductor layer is arranged between the active layer and the second p-type nitride semiconductor layer. The second p-type nitride semiconductor layer has a band gap larger than that of the first p-type nitride semiconductor layer.

Description

Nitride semiconductor device and its manufacture method

Technical field

The present invention relates to nitride semiconductor device, semiconductor light-emitting elements, the nitride semiconductor device that comprises bipolar transistor and their manufacture method that particularly a kind of expectation is used in optoelectronic information processing unit and lighting source etc.

Background technology

III-V group-III nitride semiconductor with V group element nitrogen (N) is because the size of its band gap is expected to the material as the short-wave long light-emitting element.(the GaN series semiconductor: AlGaInN), blue LED (LED), green LED have been carried out practical application to research gallium nitride series compound semiconductor wherein just in vogue.And, in order to realize the high capacity of optical disc apparatus, thirst for 400nm with on have the semiconductor laser of oscillation wavelength, that is gazed at has reached realistic scale with the GaN series semiconductor now as the semiconductor laser of material.

GaN series semiconductor laser, open flat 10-126006 communique, JapaneseJournal of Applied Physics, Vol.38, L226-L229 (1999), physica status solidi (a) 194 for example spy, No.2, open among the 407-413 (2002) etc.

Below, see figures.1.and.2, in the past GaN series semiconductor laser is described.

At first, with reference to Fig. 1 (a).

Semiconductor laser shown in Fig. 1 (a) has: low dislocation ELO-GaN substrate 101 and the stepped construction of epitaxially grown nitride-based semiconductor on ELO-GaN substrate 101.ELO-GaN substrate 101 is made of the thick film of the GaN that makes by selection transverse direction growth (Epitaxial Lateral Overgrowth).

From substrate 101 sides, the semiconductor stacked structure among Fig. 1 (a) has respectively: n-Al _0.015Ga _0.985N contact layer 102; Ga _0.95In _0.05The N crackle suppresses layer 103; N-Al _0.15Ga _0.85N/n-GaN superlattice (SLs) coating layer 104; GaN light guide layer 105; Ga _0.86In _0.14N/Ga _0.99In _0.01N multiple quantum trap (MQW) active coating 106; P-Al _0.20Ga _0.80N cap rock 107; GaN light guide layer 108; P-Al _0.15Ga _0.85N/p-GaN-SLs coating layer 109; And p-GaN contact layer 110.The crystal growth of these semiconductor layers realizes by for example using organic metal vapor growth method (MOVPE method).

Semiconductor stacked structure with said structure is processed to the shape shown in Fig. 1 (a), is formed with p electrode 111, SiO thereon ₂Layer 112 and n electrode 113.

The band structure of this semiconductor laser conduction band side is represented in Fig. 1 (b) medelling.The transverse axis of Fig. 1 (b) is corresponding to the distance of distance substrate surface, and is more near the left side among the figure, far away apart from substrate surface.The longitudinal axis is the energy level of conduction band lower end.

This semiconductor laser is characterised in that, in order to suppress In from the evaporation of active coating with suppress electronics from the overflowing of active coating in crystal growth, formed the p-Al of energy gap maximum directly over MQW active coating 106 _0.20Ga _0.80N cap rock 107.

Below, with reference to Fig. 2 (a), other GaN semiconductor laser is described.

This semiconductor laser is identical with the semiconductor laser of Fig. 1 (a), the semiconductor stacked structure that has ELO-GaN substrate 201 and form thereon.Semiconductor stacked structure has: n-GaN contact layer 202; N-Al _0.08Ga _0.92N coating layer 203; GaN light guide layer 204; Ga _0.90In _0.10N/Ga _0.98In _0.02N-MQW active coating 205; GaInN intermediate layer 206; AlGaN intermediate layer 207; P-Al _0.16Ga _0.84N electronic barrier layer 208; P-Al _0.15Ga _0.85N/p-GaN-SLs coating layer 209; And p-GaN contact layer 210.

This semiconductor stacked structure is processed to the shape shown in Fig. 2 (a), is formed with p electrode 211, SiO thereon ₂Layer 212 and n electrode 213.

Fig. 2 (b) represents the ideograph of this semiconductor laser conduction band side band structure.This semiconductor laser is characterised in that, in order to reduce the caused optical absorption loss of layer by the p type impurity that mixed as much as possible, at MQW active coating 205 and p-Al _0.16Ga _0.84Formed the wall that is called as GaInN intermediate layer 206, AlGaN intermediate layer 207 between the N electronic barrier layer 208.And, because GaInN intermediate layer 206 and AlGaN intermediate layer 207 also have the function as light guide layer, so, different with semiconductor laser shown in Fig. 1 (a), do not form the light guide layer of p side.

Reported the continuous oscillation that the GaN semiconductor laser with this structure can both be realized output 30mW under the room temperature.

But, have Fig. 1 (a) and (b) shown under the situation of semiconductor laser of structure, the AlGaN cap rock 106 that directly over the active coating 106 of lattice constant maximum, has connected the lattice constant minimum in the laser structure, then on active coating 106, apply big distortion, thereby caused uniformity and the reproducibility of laser component when making bad.

On the other hand, have Fig. 2 (a) and (b) shown under the situation of semiconductor laser of structure, between active coating 205 and AlGaN electronic barrier layer (obtain and Fig. 1 AlGaN cap rock 107 identical functions), inserted the intermediate layer.Therefore, alleviate the distortion that is applied on the active coating effectively, improved the uniformity of laser component when making.

Be jointly in these semiconductor lasers: from carry out laser structure during the growth of the AlGaN cap rock of band gap maximum (AlGaN electronic barrier layer), just begun to realize the doping of the acceptor impurity of p type crystal.

In nitride series semiconductor, use magnesium (Mg) usually as acceptor impurity.On this Mg, when the known doping when crystal growth, can be called as the phenomenon of " storage effect ".So-called " storage effect " is in crystal growth, enters into before the crystal that time delay produces owing to having taken place when doping impurity begins to the impurity that in fact is doped.More specifically, when this storage effect had taken place, the doping starting position was compared to the crystal growing surface side with the position of hope and is staggered, and made in the depth direction of impurity concentration distributes, and concentration can precipitous increase but had the foot of a mountain shape.

In addition, opposite with above-mentioned situation, i.e. " storage effect " moment, entering to the impurity that in fact is doped and to have produced time delay before finishing in the crystal from crystal growth, finish mixing.In this case, the face side that the doping end position is compared to crystal grown layer with desired location staggers, and makes in the depth direction of impurity concentration distributes, and Mg concentration can precipitous reduction but had the foot of a mountain shape.

In making Mg doping starting position and laser structure under the consistent situation in the growth starting position of the AlGaN cap rock (AlGaN electronic barrier layer) of band gap maximum, if this storage effect takes place, then in AlGaN cap rock (AlGaN electronic barrier layer), can produce the local part that reduces of Mg concentration.

Usually, have this tendency, promptly band-gap energy becomes big more, and in other words, the Al composition in the crystal becomes high more, and then the activation energy of acceptor impurity becomes big more.If postpone to have formed the low part of Mg concentration by the Mg doping that is caused by storage effect, then Mg can not activated fully in this part, thereby causes the reduction of AlGaN electronic barrier layer performance.

Open in other prior art examples that the 2000-143396 communique put down in writing the spy, when making p type GaN crystal, mixed 2 * 10 ²⁰Cm ^-3Following Al (because the degree of band-gap energy for GaN being changed, so be not the AlGaN mixed crystal).Thus, the distortion of having alleviated crystal by doped with Mg has been described, making acceptor impurity is that Mg is configured on the Ga atom site in the GaN crystal effectively, thereby has obtained high hole concentration.But, even implementing Al mixes, Mg concentration itself also is steady state value, if Al concentration is controlled to be optimization, though then can realize high hole concentration, the inhibition of the storage effect on the doped interface, acceptor impurity distribution (profile) controlled and that abruptness is high not described by the activity ratio that improvement is led.

Open in another other prior art examples that the 2002-198314 communique put down in writing the spy, in order to improve the abruptness of Mg dopant profiles, made the multiple heterostructure (superlattice structure) of AlGaN layer/GaN layer or GaInN layer/GaN layer, and carried out Mg thereon and mix.According to this method, even same doped with Mg, at the near interface of the substrate-side (growth beginning side) of the AlGaN layer or the GaInN layer of GaN layer and AlGaN layer or GaN layer and GaInN layer and heterogeneous interface, Mg concentration also can local increase.Then, by utilizing the local phenomenon that increases of this Mg concentration, improve abruptness thereby form the interface energetically.But, in the method, though abruptness has improved, the Mg doping still can take place in the big AlGaN layer of band gap postpone, make in the AlGaN layer, to have produced the inhomogeneous of Mg concentration.And, can in crystal, produce the undue and not enough of Mg concentration brokenly by forming most heterogeneous interfaces, make controlled, reproducibility is very low.

In view of the above problems, the inventor has made the laser structure shown in Fig. 3 (a).The element of Fig. 3 (a) has ELO-GaN substrate 301.ELO-GaN substrate 301 is ABLEG (Air-BridgedLateral Epitaxial Growth) substrates, has not shown gap structure.The details of ABLEG is for example opened in the 2002-009004 communique open the spy.

Semiconductor stacked structure on the substrate 301 comprises: n-GaN contact layer 302; N-Al _0.07Ga _0.93 N coating layer 303; N-GaN light guide layer 304; Ga _0.90In _0.10N/Ga _0.98In _0.02N-MQW active coating 305; GaInN intermediate layer 306; GaN intermediate layer 307; The p-GaN acceptor impurity mixes and begins layer 308; P-Al _0.16Ga _0.84The N electronics overflows and suppresses layer 309; P-Al _0.14Ga _0.86N/p-GaN-SLs coating layer 310; And p-GaN contact layer 311.The band structure of this laser structure conduction band side of Fig. 3 (b) medelling ground expression.

This laser structure is characterised in that: be not the p-Al with band gap maximum in laser structure _0.16Ga _0.84The N electronics overflows the growth that suppresses layer 309 and begins together to begin the doping of acceptor impurity, but is provided with p-GaN acceptor impurity doping beginning layer 308 before.Though in this p-GaN acceptor impurity mixes beginning layer 308, exist to result from the doping of storage effect and postpone, by considered should dopings delay thickness design, can make p-Al _0.16Ga _0.84The Mg doping content that the N electronics overflows inhibition layer 309 is certain.

But, in the growing method of these prior aries, though with the p-Al of band-gap energy maximum in the laser structure _0.16Ga _0.84The N electronics overflows the Mg concentration that suppresses layer 309 and becomes certain value, but since storage effect make mix beginning and when finishing generation time postpone, make the abruptness step-down of dopant profiles of Mg, the result is at p-Al _0.16Ga _0.84The N electronics overflows the Mg concentration of the Mg concentration about 50% to 70% of the relative coating layer that only mixed in the inhibition layer 309, and then the absolute magnitude as Mg is not enough.Therefore, reduce, make to be difficult to realize that with good reproducibility, uniformity enough low threshold currents drive to the hole of active coating injection efficiency.And, owing to stagger from the active coating position in the pn interface, cause the rising of threshold voltage.

In order to improve p-Al _0.16Ga _0.84The N electronics overflows the Mg concentration that suppresses layer 309, as long as make p-GaN-acceptor impurity doping beginning layer 308 enough thick, thus, can make p-Al _0.16Ga _0.84The Mg concentration that the N electronics overflows the Mg concentration that suppresses layer 309 to be become with coating layer is same degree.But if also have a lot of Mg in the p-GaN-acceptor impurity mixes beginning layer 308, electric current that applies during then owing to laser works and heat and the magnetic field that is applied on the laser will cause Mg easily to be diffused into the active coating side.Its result, Mg arrive near the active coating, can cause optical absorption loss near active coating, thereby the reliability of laser is produced bad influence, the feasible laser component that is difficult to realize reproducibility, have good uniformity and have high reliability.

Summary of the invention

In view of the above problems, the invention provides the nitride semiconductor device that a kind of rate of finished products is good, reliability is high.

Nitride semiconductor device of the present invention is to comprise: p type nitride semiconductor layer, n type nitride semiconductor layer and be clamped in described p type nitride semiconductor layer and described n type nitride semiconductor layer between the nitride semiconductor device of active coating, described p type nitride semiconductor layer has: a p type nitride semiconductor layer that comprises Al and Mg, the 2nd p type nitride semiconductor layer that comprises Mg, a described p type nitride semiconductor layer is between described active coating and described the 2nd p type nitride semiconductor layer, and described the 2nd p type nitride semiconductor layer has the big band gap of band gap than a described p type nitride semiconductor layer.

In a preferred embodiment, described the 2nd p type nitride semiconductor layer plays a part the barrier layer of overflowing as the charge carrier that suppresses from described active coating.

In a preferred embodiment, the Al concentration of a described p type nitride semiconductor layer is 1 * 10 ²⁰Cm ^-3More than 2 * 10 ²¹Cm ^-3Below, Al concentration is 1 * 10 in the described p type nitride semiconductor layer ²⁰Cm ^-3More than 2 * 10 ²¹Cm ^-3The thickness in following zone is more than the 1nm.

In the preferred implementation, also comprise between a described p type nitride semiconductor layer and described active coating and comprise Al non-ly ooze assorted nitride semiconductor layer.

In the preferred implementation, describedly non-ly ooze assorted nitride semiconductor layer and have the little band gap of band gap than described the 2nd p type nitride semiconductor layer.

In the preferred implementation, the described non-nitride semiconductor layer of mixing that oozes has the band gap that equates with the band gap of a described p type nitride semiconductor layer.

In the preferred implementation, the described non-aggregate thickness that oozes an assorted nitride semiconductor layer and a described p type nitride semiconductor layer is below the above 50nm of 1nm.

In the preferred implementation, the thickness of described the 2nd p type nitride semiconductor layer is below the above 20nm of 5nm.

In the preferred implementation, in described the 2nd p type nitride semiconductor layer, Mg concentration is 8 * 10 ¹⁸Cm ^-3The thickness in following zone is below the 1nm.

In the preferred implementation, described p type nitride semiconductor layer also has the 3rd p type nitride semiconductor layer, it has the little band gap of band gap than described the 2nd p type nitride semiconductor layer, and described the 2nd p type nitride semiconductor layer is between described the 3rd a p type nitride semiconductor layer and a described p type nitride semiconductor layer.

In the preferred implementation, the band gap of described the 3rd p type nitride semiconductor layer is littler than the band gap of a described p type nitride semiconductor layer.

In the preferred implementation, described the 3rd p type nitride semiconductor layer plays a part coating layer.

In the preferred implementation, at least one side of a described p type nitride semiconductor layer and described the 2nd p type nitride semiconductor layer comprises In.

In the preferred implementation, the In ratio of components of described the 2nd p type nitride semiconductor layer is bigger than the In ratio of components of a described p type nitride semiconductor layer.

Manufacture method according to nitride semiconductor device of the present invention, wherein, nitride semiconductor device comprises: p type nitride semiconductor layer, n type nitride semiconductor layer, and be clamped in active coating between described p type nitride semiconductor layer and the described n type nitride semiconductor layer, described p type nitride semiconductor layer has: a p type nitride semiconductor layer that comprises Al and Mg, and the 2nd p type nitride semiconductor layer that comprises Mg, a described p type nitride semiconductor layer is between described active coating and described the 2nd p type nitride semiconductor layer, described the 2nd p type nitride semiconductor layer has the big band gap of band gap than a described p type nitride semiconductor layer, and this method comprises: the operation that forms described n type nitride semiconductor layer; Form the operation of described active coating; By supplying with unstrpped gas simultaneously and having the unstrpped gas of Al, form the operation of a described p type nitride semiconductor layer that comprises Al and Mg with Mg; And the operation that forms described the 2nd p type nitride semiconductor layer by the unstrpped gas that supply has a Mg.

In the preferred implementation, also comprise: before forming the operation of a described p type nitride semiconductor layer, by not supplying with p type impurity but supply with and have the unstrpped gas of Al, form the non-operation of oozing assorted nitride semiconductor layer that comprises Al.

In the preferred implementation, the Al concentration of a described p type nitride semiconductor layer is 1 * 10 ²⁰Cm ^-3More than 2 * 10 ²¹Cm ^-3Below, Al concentration is 1 * 10 in the described p type nitride semiconductor layer ²⁰Cm ^-3More than 2 * 10 ²¹Cm ^-3The thickness in following zone is more than the 1nm.

Description of drawings

Fig. 1 (a) is the cutaway view of expression GaN semiconductor laser prior art example, and Fig. 1 (b) is the ideograph of its conduction band side band structure.

Fig. 2 (a) is the cutaway view of another prior art example of expression GaN semiconductor laser, and Fig. 2 (b) is the ideograph of its conduction band side band structure.

Fig. 3 (a) is the cutaway view of the another prior art example of expression GaN semiconductor laser, and Fig. 3 (b) is the ideograph of its conduction band side band structure.

Fig. 4 (a) is the sectional structure chart of the nitride semi-conductor laser in the embodiment of the present invention 1, and Fig. 4 (b) is the ideograph of its conduction band side band structure.

Fig. 5 (a) be presentation graphs 3 (a) and (b) shown in semiconductor laser in the SIMS distribution curve, Fig. 5 (b) be the expression execution mode 1 semiconductor laser in the SIMS distribution curve.

Fig. 6 is the Al composition that expression is mixed and begun layer with respect to the p-AlGaN-acceptor impurity, and the p-AlGaN electric current overflows the curve of the Mg concentration that suppresses layer.

Fig. 7 (a) is the cutaway view of the semiconductor laser in the expression embodiment of the present invention 3, and Fig. 7 (b) is the ideograph of the conduction band side band structure of comparative example, and Fig. 7 (c) is the ideograph of the conduction band side band structure in the present embodiment.

Fig. 8 (a) is the cutaway view of the semiconductor laser in the expression embodiment of the present invention 4, and Fig. 8 (b) is the ideograph of its conduction band side band structure.

Fig. 9 (a) is the cutaway view of the semiconductor laser in the expression embodiment of the present invention 5, and Fig. 9 (b) is the ideograph of its conduction band side band structure.

Figure 10 (a) is the cutaway view of the semiconductor laser in the expression embodiment of the present invention 6, and Figure 10 (b) is the ideograph of its conduction band side band structure.

Figure 11 (a) is the cutaway view of the semiconductor laser in the expression embodiment of the present invention 7, and Figure 11 (b) is the ideograph of its conduction band side band structure.

Figure 12 is the cutaway view of the semiconductor laser in the expression embodiment of the present invention 8.

Figure 13 is near the ideograph of conductor band structure the active coating in the semiconductor laser of expression execution mode 8.

Figure 14 is the cutaway view of the semiconductor laser in the expression embodiment of the present invention 9.

Figure 15 is near the ideograph of conductor band structure the active coating in the semiconductor laser of expression execution mode 9.

Figure 16 is near the ideograph of other conductor band structures the active coating in the semiconductor laser of expression execution mode 9.

Embodiment

Below, with reference to accompanying drawing, embodiments of the present invention are described.

(execution mode 1)

First execution mode of nitride semiconductor device of the present invention at first, is described.

The cross-section structure of the semiconductor laser of Fig. 4 (a) expression present embodiment, Fig. 4 (b) is the ideograph of its conduction band side band structure.The semiconductor laser of present embodiment has: n-GaN substrate 401 and the semiconductor stacked structure that forms on n-GaN substrate 401.This semiconductor stacked structure begins to have from substrate-side: n-GaN layer 402; N-Al _0.05Ga _0.95 N coating layer 403; N-GaN light guide layer 404; Ga _0.90In _0.10N/Ga _0.98In _0.02N-MQW active coating 405; The non-Ga that mixes that oozes _0.98In _0.02N intermediate layer 406; The non-GaN intermediate layer 407 of mixing of oozing; The non-Al that mixes that oozes _0.03Ga _0.97N intermediate layer 408; P-Al _0.03Ga _0.97The N acceptor impurity mixes and begins layer 409; P-Al _0.16Ga _0.84The N electronics overflows and suppresses layer 410; P-Al _0.10Ga _0.90N (2nm is thick)/p-GaN (2nm is thick)-SLs coating layer (120 pairs) 411; And p-GaN contact layer 412.

Here, p-Al _0.03Ga _0.97N acceptor impurity doping beginning layer 409 plays a part " comprising the p type nitride semiconductor layer of Al and Mg ", p-Al _0.16Ga _0.84The N electronics overflows inhibition layer 410 and plays a part " comprising the 2nd p type nitride semiconductor layer of Mg ".

Shown in Fig. 4 (b), p-Al _0.03Ga _0.97The band gap of N acceptor impurity doping beginning layer 409 compares p-Al _0.16Ga _0.84The band gap that the N electronics overflows inhibition layer 410 is little, compares p-Al _0.10Ga _0.90The maximum of the band gap in N (2nm is thick)/p-GaN (2nm is thick)-SLs coating layer (120 pairs) 411 is also little.

This semiconductor stacked structure is processed to the shape shown in Fig. 4 (a), is formed with p electrode 413, n electrode 414 and SiO thereon ₂ Layer 415.

In this semiconductor laser, if between n electrode 414 and p electrode 413, apply voltage, then the hole is injected into MQW active coating 405 from p electrode 13, electronics from n electrode 414, produces gain in MQW active coating 405, and produces laser generation with the 410nm wavelength.

Below, the execution mode of semiconductor laser fabrication method shown in the key diagram 4 (a).

In the present embodiment, use the MOVPE method to carry out the crystal growth of nitride semiconductor layer.Growth pressure can be any one in the above pressurization of decompression, atmospheric pressure (1atm), atmospheric pressure, also can switch to only pressure in each layer.In addition, the carrier gas that is used to supply raw material into substrate is preferably and comprises nitrogen (N at least ₂) or hydrogen (H ₂) gas of the inert gas that waits.

In addition, nitride semiconductor growth method of the present invention is not limited to the MOVPE method, and hydride vapor growth method (HVPE method) or molecular beam epitaxy (MBE method) etc. all are to be applicable to the method that generates compound semiconductor crystal.

In the present embodiment, at first, after the surface of n-GaN substrate 401 being cleaned, it is arranged on pedestal (suscepter) goes up and pass through N by organic solvent, acid ₂Replace fully.At N ₂After the replacement completion, at N ₂In the atmosphere, be warmed up to 1000 ℃ with 10 ℃/10 seconds heating rates.Afterwards, carrier gas is switched to H ₂, supply with ammonia (NH simultaneously ₃), the cleaning (cleaning) that comes 1 minute substrate surface of row.

Then, supply with trimethyl gallium (TMG) and monosilane (SiH ₄), the thick n-GaN layer 402 of 2 μ m of growing.Then, add trimethylaluminum (TMA), the thick n-Al of 1.5 μ m grows _0.05Ga _0.95N coating layer 403.After this, stop the supply of TMA, growth thickness is the n-GaN light guide layer 404 of 0.1 μ m.

After 404 growths of n-GaN light guide layer, carrier gas is become N ₂, stop NH ₃Supply, and growth temperature is reduced to 780 ℃.Be stabilized in after 780 ℃ in growth temperature, at first supply with NH ₃, then supply with TMG and trimethyl indium (TMI).Like this, can generate Ga _0.90In _0.10N/Ga _0.98In _0.02N-MQW active coating 405.Ga _0.90In _0.10N trap bed thickness is 3nm, Ga _0.98In _0.02N potential barrier bed thickness is 7nm, and the trap number of plies is 3.On active coating, do not carry out intentional doping.

Then, at the thick non-Ga that mixes that oozes of 30nm that grown _0.98In _0.02Non-the oozing after the assorted GaN intermediate layer 407 that N intermediate layer 406 and 30nm are thick stops the supply of TMG for the time being.After this, supplying with N ₂And NH ₃State under promptly be warmed up to 1000 ℃, after growth temperature arrives 1000 ℃, carrier gas is altered to N ₂And H ₂Mist, become and supply with N ₂, H ₂And NH ₃State.

Then, by directly supplying with TMG and TMA, the non-Al that mixes that oozes that the 40nm that grows is thick _0.03Ga _0.97Magnesium (Cp afterwards, is closed with dicyclopentadiene in N intermediate layer 408 ₂Mg) as the Mg raw material, and the p-Al of the Mg that mixed _0.03Ga _0.97N acceptor impurity doping beginning layer 409 grows into thickness 5nm.

Then, at the p-Al of 10nm thickness that grown _0.16Ga _0.84The N electronics overflows and suppresses after the layer 410, and promptly carrier gas being switched to only is H ₂, come stacked above one another p-Al _0.10Ga _0.90N (2nm is thick)/p-GaN (2nm is thick)-SLs coating layer (120 pairs) 411 and the thick p-GaN contact layer 412 of 50nm.

Then, with p-Al _0.03Ga _0.97The N acceptor impurity mixes and begins layer 409, p-Al _0.16Ga _0.84The N electronics overflows and suppresses layer 410, p-Al _0.10Ga _0.90N/p-GaN-SLs coating layer 411 and p-GaN contact layer 412 are processed into lines (stripe) shape.Afterwards, will be processed to the both sides of banded stepped construction by SiO as dielectric film ₂Layer 415 covers, and forms the current injection area territory.Line thickness is about 2～3 microns.

Then, at SiO ₂The surface and the SiO of the p-GaN contact layer 412 of layer 415 peristome ₂Form p electrode 413 on the part of layer 415.Afterwards, make after the part of n-GaN layer 402 exposes, on its exposing surface, form n electrode 414 in stepped construction by etching semiconductor.Also can substitute such way, form the n electrode at the back side of n-GaN substrate.

In the present embodiment, in order to reduce the contact resistance with p electrode 413, with the Mg concentration adjustment of p-GaN contact layer 411 1 * 10 ²⁰Cm ^-3To 5 * 10 ²⁰Cm ^-3Scope in.

According to above-mentioned manufacture method, growth is non-ooze assorted GaN intermediate layer 407 after, ooze assorted Al in that growth is non- _0.03Ga _0.97During the N intermediate layer 408, temporarily stop the supply of TMG.Then, supplying with N ₂And NH ₃State under promptly heat up, and halfway carrier gas is changed to N ₂And H ₂Mist.

But, also can not stop the supply of TMG, sustainable supply TMG continues non-crystal growth of oozing assorted GaN intermediate layer 407, and heats up.And, can also supply with TMG and TMA, Yi Bian carry out the non-assorted Al that oozes _0.03Ga _0.97The crystal growth in N intermediate layer 408 heats up on one side.Like this, if in crystal, do not generate method, then can adopt any temperature-rising method as the defective of the reason of non-radiative recombination center.

Below, the non-assorted A1 that oozes is described _0.03Ga _0.97N intermediate layer 408 and p-Al _0.03Ga _0.97The N acceptor impurity mixes and begins 409 couples of p-Al of layer _0.16Ga _0.84The effect that the Mg CONCENTRATION DISTRIBUTION that suppresses layer 410 of overflowing the N electronics is played.

Fig. 5 (a) be presentation graphs 3 (a) and (b) shown in semiconductor laser in the SIMS distribution curve, Fig. 5 (b) is the curve that the SIMS in the semiconductor laser of expression present embodiment distributes, the semiconductor laser of present embodiment is at growth p-Al _0.16Ga _0.84The N electronics overflows and suppresses before the layer 410, has formed the non-assorted Al that oozes _0.03Ga _0.97N intermediate layer 408 and p-Al _0.03Ga _0.97The N acceptor impurity mixes and begins layer 409.In addition, in curve, " 1.0E+M " means " 1.0 * 10 ^M".

In Fig. 5 (a) and any one sample (sample) (b), all carry out Mg and mix, make p type coating layer (p-Al _0.10Ga _0.90N/p-GaN-SLs coating layer 411 and p-Al _0.14Ga _0.86N/p-GaN-SLs coating layer 310) hole concentration becomes 2 * 10 ¹⁸Cm ^-3Particularly, be 1 * 10 with Mg concentration in the p type coating layer ¹⁹Cm ^-3Condition carry out the doping of Mg.

The thickness unification of P type acceptor impurity doping beginning layer 409 is 5nm, and electronics overflows the unified 10nm of being of thickness of inhibition layer 410.In the semiconductor laser of present embodiment, from the CONCENTRATION DISTRIBUTION of the Mg shown in Fig. 5 (b) as can be known, the AlGaN electronics overflows the Mg concentration that suppresses layer 410 and has reached 9.5 * 10 ¹⁸Cm ^-3, realized being substantially equal to the desired value (1 * 10 of Mg concentration in the coating layer 411 ¹⁹Cm ^-3).Relative therewith, in the example of Fig. 5 (a), the doping delayed impact that causes owing to storage effect that Mg mixes has appearred significantly.That is, overflow at the AlGaN electronics and suppress that Mg concentration changes in the layer 309 on depth direction, its size also has only 5～7 * 10 ¹⁸Cm ^-3About.

As mentioned above, ooze assorted Al comprise Al non-that grown _0.03Ga _0.97N intermediate layer 408 and p-Al _0.03Ga _0.97The N acceptor impurity mixes and begins after the layer 409, by growth p-Al _0.16Ga _0.84The N electronics overflows and suppresses layer 410, and the doping that can suppress the Mg that causes because of storage effect postpones.Consequently, can make the p-Al of band-gap energy maximum in the laser structure _0.16Ga _0.84It is almost equal that the N electronics overflows the Mg concentration and the Mg concentration in the coating layer 401 that suppress in the layer 410.

In order to obtain the effect of present embodiment, after beginning Mg mixes, preferably will overflow the thickness that suppresses " nitride semiconductor layer (a p type nitride semiconductor layer) that comprises Al " that layer 410 (the 2nd p type nitride semiconductor layer) are grown before and form below the above 50nm of 1nm beginning growth.For the Al concentration in the nitride semiconductor layer (a p type nitride semiconductor layer) that comprises Al at this is high fully, the Al concentration in the preferred p type nitride semiconductor layer is 1 * 10 ²⁰Cm ^-3More than 2 * 10 ²¹Cm ^-3Below, and in a p type nitride semiconductor layer, Al concentration is 1 * 10 ²⁰Cm ^-3More than 2 * 10 ²¹Cm ^-3The thickness in following zone is preferably more than the 1nm.

Mg finally from a p type nitride semiconductor layer be diffused into growth carry out before the one p type nitride semiconductor layer comprise Al non-ly ooze assorted nitride semiconductor layer (Al _0.03Ga _0.97N intermediate layer 408) in, there is the possibility that comprises p type zone in the result.But, for simply, in this manual as long as be not intentional ground doped p type impurity constantly, just with Al in growth _0.03Ga _0.97N intermediate layer 408 is called " comprise Al non-ooze assorted nitride semiconductor layer ".

Substitute Ga and use the p-Al that comprises In _0.90In _0.10N acceptor impurity doping beginning layer also can obtain the effect by the present embodiment acquisition.In this case, importantly with respect to the p-Al of band-gap energy maximum in the laser structure _0.16Ga _0.84The N electronics overflows and suppresses layer 410, and little (but and the Ga of band-gap energy is compared in formation with it _0.90In _0.10N/Ga _0.98In _0.02It is big that N-MQW active coating 405 is compared its band-gap energy), and the non-acceptor impurity that oozes assorted intermediate layer and comprise Al at least that comprises Al at least beginning layer this 3-tier architecture that mix.The necessity that comprises Al will be narrated in the back.

In addition, open in the semiconductor laser that the 2002-009004 communique put down in writing, spread from the AlGaN layer in order to prevent Mg, at Mg doping p-AlYGa the spy _1-YInserted the non-assorted Al that oozes between N layer and the Si Doped n-GaN layer _xGa _1-xN layer (0≤X≤Y≤1).In this constitutes, by inserting the non-assorted Al that oozes _xGa _1-xThe N layer has suppressed Mg from the Mg p-Al that mixes _YGa _1-YThe diffusion of N course active coating (Si Doped n-GaN layer).It is luminous that the purpose that suppresses the Mg diffusion is to suppress alms giver's/led pairing, thereby arrange can band edge luminous.

In above-mentioned semiconductor laser, because the Mg doping p-Al of band-gap energy maximum in the relative laser structure _YGa _1-YN layer and having formed is formed with and has used the non-assorted Al that oozes _x Ga _1-x2 layers of structure of N layer are so can suppress the diffusion of Mg impurity.But, the Mg doping p-Al of band-gap energy maximum in laser structure _YGa _1-YHaving produced the Mg doping that causes because of storage effect on the N layer postpones.

In addition, according to the present application people's research as can be known, with the Mg doping p-GaN layer that does not comprise Al relatively, Mg is not easy to take place from the diffusion of the Mg doping p-AlGaN course active coating that comprises Al very much.The details of this point will be narrated in the back.

Certainly, owing to compare with the band-gap energy of GaN, the band-gap energy of AlGaN that contains Al is bigger, so that the activation energy of the acceptor impurity among the AlGaN becomes relatively is big.Therefore, if the doping of beginning Mg in AlGaN growth then owing to be not easy to make the impurity activation of p type, thereby makes reproducibility, uniformity reduce, the therefore not preferably doping of beginning Mg in the AlGaN growth.

And owing to compare with the lattice constant difference between AlGaN and the GaN, it is big that lattice constant difference between AlGaN and the GaInN becomes, so, when the AlGaN layer being configured near active coating, cause the inhomogeneous of the trap layer distortion that constitute active coating easily.If should distortion become big, then can exert an adverse impact to the characteristics of luminescence, be undesirable for uniformity and reliability.

But,,, can successfully reduce the storage effect that Mg mixes, and can realize the doped interface that abruptness is high, thereby can improve the characteristics of luminescence of laser significantly by Al specially is included among the GaN according to present inventor's result of study.

In addition, in order to be reduced in the lattice deformability that takes place in the trap layer, preferably with non-size of oozing the thickness setting in assorted GaN intermediate layer in optimum reduction distortion.

Below, the effect of Al in the beginning layer that mixes is described.

Mg is that raw material is very easy on the pipe arrangement and reactor (reactor) inwall attached to crystal growing apparatus, and at the initial stage after beginning to mix, raw material mostly is consumed in this reaction.This is the main cause that produces storage effect.The influence of storage effect also depends on crystal growing apparatus, but in the employed crystal growing apparatus of present embodiment, in order in the GaN growth, to obtain 1 * 10 ¹⁹Cm ^-3Mg concentration, when beginning Mg mixed, the doping front end (front) of Mg moved about 10nm in the plane of crystal lateral deviation.Therefore, Mg concentration reaches 1 * 10 ¹⁹ Cm ^-390% level (9 * 10 ¹⁸Cm ^-3), be exactly after beginning GaN growth, carry out the moment that thickness is the crystal growth about 200nm.

On the other hand, when carrying out same Mg doping in the AlGaN that consists of 1% at Al grows, the delay of Mg doping wavefront can not take place, and reach 9 * 10 ¹⁸Cm ^-3Mg concentration only want 10nm.This is because because the reactivity of Mg and Al is very high, so when adding Mg in the unstrpped gas that is containing Al, Al and Mg can immediate responses, formation can not enter in the crystal attached to the complex on pipe arrangement and the reactor wall.

Below, with reference to Fig. 6.Fig. 6 is the Al composition that expression is mixed and begun layer with respect to the p-AlGaN acceptor impurity, and the p-AlGaN electric current overflows the curve of the Mg concentration that suppresses layer.As shown in Figure 6, the Al concentration in the p-AlGaN-acceptor impurity doping beginning layer is preferably set to the size more than 10 times of Mg doping content.Particularly, Mg concentration if necessary is 1 * 10 ¹⁹Cm ^-3, then preferred Al concentration is 1 * 10 ²⁰Cm ^-3, the Al in the crystal forms and is set at more than 0.1%.If mix A concentration in the beginning layer of p-AlGaN-acceptor impurity is set in the size more than 100 times of Mg doping content, then Mg concentration can further increase, and is therefore more preferred.

As mentioned above, carry out Mg by the complex that forms Al and Mg expeditiously and mix, can suppress the storage effect of Mg.Its result can realize having the Mg dopant profiles that precipitous doped interface is not mixed and postponed.

In addition, begin layer 308 by GaN intermediate layer 307 and the doping of p-GaN acceptor impurity that substitutes in the semiconductor laser shown in Figure 3, and use the non-assorted Al that oozes _0.03Ga _0.97N intermediate layer 408 and p-Al _0.03Ga _0.97The N acceptor impurity mixes and begins layer 409, can reduce the compression stress when the formation electronics overflows the inhibition layer.

Compression stress can produce piezoelectric field, and the variation of the band structure that causes owing to it makes the acceptor impurity diffusion, forms uneven CONCENTRATION DISTRIBUTION.But, in the present embodiment, comprise the mix combination of beginning layer of the intermediate layer/acceptor impurity that can make the Al that compression stress reduces by use, can effectively realize the Mg dopant profiles that abruptness is good.

The formed acceptor level of Mg in the GaN crystal is that the activation energy of Si is big than donor impurity.Therefore, when making the laser vibration by the electric current injection, optical loss (optical absorption loss) takes place easily.But, in the present invention, owing to can controlled with height, high abruptness come on the interface, to form the dopant profiles of wishing, so, can provide optical absorption loss extremely low laser component with better rate of finished products.

In addition, mix and realize the method for abrupt dopant distribution, also consider the method that only on doped interface, makes Mg quantity delivered surplus come controlled doping to postpone as beginning Mg in the p-GaN layer.But pipe arrangement and reactor wall adhere to and can not reduce, and the doping that is caused by storage effect postpones still can take place, and overflow at the AlGaN electronics that to suppress in the layer acceptor impurity be Mg on the contrary and got by excessive drawing that (for example Mg concentration is 1 * 10 ²⁰Cm ^-3More than), make to be subjected to main the compensation, cause high resistanceization, thereby lack controlled.

And, though crystal growing apparatus can be transformed into pipe arrangement, the structure of reactor that is difficult to take place storage effect,, the time of its cost and needs also is huge for this reason.

In contrast, according to the present invention, plant modification and method just can easily improve controlled that Mg mixes especially.

In order to obtain effect of the present invention, Yi Bian carry out the Mg doping on one side importantly form the complex of Al and Mg expeditiously.When carrying out the Mg doping, if carrier gas not only comprises H ₂Also comprise N ₂, then because reactive high, therefore preferred.And in order to improve this reactivity, in not influencing the electrical characteristics scope of laser structure, it also is effective that trace adds impurity such as oxygen, carbon, silicon.

Using in the past p-GaN acceptor impurity to mix under the situation of beginning layer,, making the Mg to be diffused into the active coating side easily owing to apply heat and the magnetic field that electric current, laser are applied in during laser works.Its result can cause the light absorption damage, thereby the reliability of laser is exerted an adverse impact near active coating.To this, using p-AlGaN acceptor impurity doping beginning layer to make under the situation of laser structure, be coupled securely in crystal Al and Mg, be difficult to when laser works, take place the diffusion of Mg.

And, under the situation of using p-GaN acceptor impurity doping beginning layer in the past, pipe arrangement and the accompanying Mg of reactor wall at crystal growing apparatus also can be residual after crystal growth, when next making laser structure, can slowly sneak into n type layer, compensate n type donor impurity and caused high resistanceization.To this,, can suppress this influence using p-AlGaN acceptor impurity doping beginning layer to make under the situation of laser structure.

Though used the GaN substrate in the present embodiment, but substrate is not limited to GaN, also can be nitride-based semiconductor bulk (bulk) substrates such as AlGaN, InGaN or AlGaInN, sapphire substrate, silicon carbide substrate, silicon substrate, from the teeth outwards grown GaN gallium arsyl plate, use the growth of selectivity transverse direction and the ELO-GaN substrate made.

In the present embodiment, though at the AlGaN that has used bulk crystals on the n type coating layer, on p type coating layer, used the superlattice structure that constitutes by AlGaN and GaN, also can use the AlGaN of bulk crystals on the p type coating layer, on n type coating layer, use the superlattice structure that constitutes by AlGaN and GaN.And, can also all use the AlGaN of bulk crystals or the superlattice structure that constitutes by AlGaN and GaN on both in n type, p type.And these semiconductor layers can also comprise In and boron (B) arsenic (As), phosphorus (P), as long as can realize the sealing of light and charge carrier effectively.

And, in the present embodiment, though use TMG as the raw material of Ga, TMA as the raw material of Al, TMI raw material, Cp as In ₂Mg is as raw material and the NH of Mg ₃As the raw material of N, still, unstrpped gas is not limited to these.Also can be with triethyl-gallium (TEG) or gallium chloride (GaCl or GaCl ₃) be used as the raw material of Ga, with triethyl aluminum (TEA) or dimethyl hydrogenation aluminium (DMAH), dimethylaluminum chloride (DMACl), trimethylamine groups aluminium alkane (TMAA) raw material as Al, with the raw material of triethylindium (TEI), two ethyl cyclopentadiene are closed magnesium (EtCp as In ₂Mg) or two methyl cyclopentadiene close magnesium (EeCp ₂Mg) as the Mg raw material, and with hydrazine (N ₂H ₄) or monomethyl hydrazine (MMH), dimethylhydrazine (DMH) be used as the raw material of N.

Particularly in order to realize the present invention effectively, importantly form the complex of Al and Mg efficiently and use it to carry out the Mg doping, because the big more effect of molecular weight is effective more in the formation of this complex, so, further preferably in the scope that can use, use the big raw material of molecular weight as much as possible.

(execution mode 2)

In the present embodiment, identical with execution mode 1 formed semiconductor stacked structure after, by the dry etching operation this stepped construction is processed into band shape.At this moment, at the non-Al that mixes that oozes _0.03Ga _0.97Before N intermediate layer 408 is about to expose, begin etching p-GaN contact layer 412, p-Al in turn from face side _0.10Ga _0.90N/p-GaN-SLs coating layer 411, p-Al _0.16Ga _0.84The N electronics overflows and suppresses layer 410, p-Al _0.03Ga _0.97The N acceptor impurity mixes and begins layer 409.Etching depth is defective (kink) grade of decision laser and the important parameter of beam shape, therefore wishes to carry out precision control.

Several positions of laser structure epitaxial wafer (epiwafer) are provided with the optical assessment besel at 50um angle, Yi Bian carry out the dry etching operation, Yi Bian optical assessment is carried out in observation, implement dry etching then and there.

In the present embodiment, carried out photoluminescence measurement as the optical assessment method.In the luminescence generated by light evaluation, used the He-Cd laser of wavelength 325nm.In the compound semiconductor that has been doped p type acceptor impurity, formed p type acceptor impurity level, observation alms giver's/led pairing is luminous, and in the compound semiconductor that is not doped p type acceptor impurity, main observation comes near the self energy band edge luminous.Do not using p-Al _0.03Ga _0.97The N acceptor impurity mixes and begins in the prior art of layer 409, and the dopant profiles that the p type is led forms the foot of a mountain shape, because doped interface is indeterminate, so can not try to achieve doped interface by optical assessment.

But, as enforcement mode 1, by using p-Al _0.03Ga _0.97The N acceptor impurity mixes and begins layer 409, can improve the abruptness of doped interface, makes and can carry out film thickness monitoring easily by optical assessment.Certainly, this control method is not only photoluminescence measurement, so long as the method that can estimate also can be used any methods such as plasma luminescence analysis.And optical assessment can not make the rate of finished products of element reduce in wafer with besel, as long as and can carry out optical assessment, no matter then its shape and size all can.

And, after etching finishes, by carry out the measurement of luminescence generated by light with besel from this optical assessment, can estimate the emission wavelength of active coating, in the last stage of laser operation, can also carry out the ocular estimate of laser structure, can realize the high efficiency that element is handled.

(execution mode 3)

Form except p type coating layer structure the laser structure that has same formation with execution mode 1 by crystal growth.Though in execution mode 1, used p-Al _0.10Ga _0.90N/p-GaN-SLs coating layer 411, but here it is substituted, use p-Al _0.08Ga _0.92N/p-Al _0.02Ga _0.98N-SLs coating layer 601.Fig. 7 (a) represents the structural map of this laser structure.

Using p-Al _0.10Ga _0.90Under the situation of N/p-GaN-SLs coating layer 411, form AlGaN layer/GaN layer by periodically repeating supply with/not supply with TMA.At this moment, mix, then in the GaN layer forms, can reduce the amount of being taken into of Mg because of storage effect if similarly carry out Mg.On the contrary when forming the AlGaN layer, will increase sharp in the amount of being taken into of near interface Mg.Therefore, because the variation that tends towards stability towards constant value repeatedly shown in Fig. 7 (b), makes Mg concentration unstable in coating layer, need to adjust repeatedly, therefore for the low voltage operating of laser structure, its reproducibility will reduce.

On the other hand, using p-Al _0.08Ga _0.92N/p-Al _0.02Ga _0.98Under the situation of N-SLs coating layer 601, sustainable supply TMA can make the influence of storage effect reduce.Therefore, shown in Fig. 7 (c), the Mg concentration in the coating layer can be controlled to be steady state value, make reproducibility good, thereby can be with the high controlled reduction that realizes operating voltage.

(execution mode 4)

Below, with reference to Fig. 8 (a) and (b), the 4th execution mode of nitride semiconductor device of the present invention is described.The semiconductor laser of present embodiment has and the identical formation of semiconductor laser (execution mode 1) shown in Fig. 4 (a) except the part that the following describes.That is the thick non-Al that mixes that oozes of the 40nm in the replacement execution mode 1, _0.03Ga _0.97The p-Al that N intermediate layer 408 and 5nm are thick _0.03Ga _0.97The N-acceptor impurity mixes and begins layer 409, has the thick non-Al that mixes that oozes of 40nm _0.03Ga _0.95In _0.02The p-Al that N intermediate layer 701 and 5nm are thick _0.03Ga _0.95In _0.02The N acceptor impurity mixes and begins layer 702.

Because the Al in these layers forms, between present embodiment and execution mode 1, equate, so, concerning the Mg dopant profiles, there is not difference, still, only make the band gap energy diminish owing to contain In.Its result, the activation energy of the impurity in these layers diminishes, thus hole concentration uprises.And the distortion that is applied on the active coating also diminishes.Therefore, according to present embodiment, can further realize reducing threshold current and improve reliability.

(execution mode 5)

Below, with reference to Fig. 9 (a) with the 5th execution mode of nitride semiconductor device of the present invention (b) is described.The semiconductor laser of present embodiment has and the identical formation of semiconductor laser (execution mode 1) shown in Fig. 4 (a) except the part that the following describes.That is, in the present embodiment, replace the thick p-Al of 5nm in the execution mode 1 _0.03Ga _0.97The N-acceptor impurity mixes and begins layer 409, has the thick p-Al of 5nm _0.03Ga _0.95In _0.02The N acceptor impurity mixes and begins layer 801 and the thick p-Ga of 5nm _0.98In _0.02N layer 802.

The mix Al of beginning layer 801 of Mg forms in two execution modes and equates, so the Mg dopant profiles do not have difference, still, in the present embodiment, owing to inserted p-Ga _0.98In _0.02So N layer 802 is MQW active coating 405 and p-Al _0.16Ga _0.84The N electronics overflows the distance that suppresses between the layer 410 and has increased corresponding amount.But, because the thick p-Ga of 5nm _0.98In _0.02N layer 802 contains In, so its band-gap energy is littler than the band-gap energy of GaN, the result has very high hole concentration.Therefore, improved injection efficiency, can further realize reducing threshold current and improve reliability to the hole of active coating 405.

(execution mode 6)

Below, with reference to Figure 10 (a) with the 6th execution mode of nitride semiconductor device of the present invention (b) is described.The semiconductor laser of present embodiment has and the identical formation of semiconductor laser (execution mode 1) shown in Fig. 4 (a) except the part that the following describes.That is, in execution mode, replace the thick non-Al that mixes that oozes of 40nm in Fig. 4 (a) semiconductor laser _0.03Ga _0.97The p-Al that N intermediate layer 408 and 5nm are thick _0.03Ga _0.97The N acceptor impurity mixes and begins layer 409, has the thick non-Al that mixes that oozes of 40nm _0.06Ga _0.84In _0.10The p-Al that N intermediate layer 901 and 3nm are thick _0.06Ga _0.84In _0.10The N acceptor impurity mixes and begins layer 902.

In the present embodiment, the mix Al of beginning layer 902 of intermediate layer 901 and acceptor impurity forms respectively and to form high than the mix Al of beginning layer 409 of the intermediate layer in the execution mode 1 408 and acceptor impurity.Therefore, because the dopant profiles of Mg rises more precipitously, so can make p-Al _0.06Ga _0.84In _0.10The N acceptor impurity mixes and begins layer 902 attenuation.

And, because the p-Al of present embodiment _0.06Ga _0.84In _0.10N acceptor impurity mix beginning layer 902 and GaN lattice match, so, can make the little of the deformation ratio execution mode 1 that is applied on the active coating 405.Therefore, can further realize high outputization and raising reliability.

(execution mode 7)

Below, with reference to Figure 11 (a) with the 7th execution mode of nitride semiconductor device of the present invention (b) is described.The semiconductor laser of present embodiment has and the identical formation of semiconductor laser (execution mode 1) shown in Fig. 4 (a) except the part that the following describes.That is, in execution mode, replace the thick non-Al that mixes that oozes of 40nm _0.03Ga _0.97The p-Al that N intermediate layer 408 and 5nm are thick _0.03Ga _0.97The N-acceptor impurity mixes and begins layer 409, has the thick non-Al that mixes that oozes of 40nm _0.01Ga _0.99N intermediate layer 1001, and the Al composition rises 0.03 up to the thick Al of 0.13 5nm from 0.01 by every 1nm ladder ground _xGa _1-xN (0.01≤x≤0.13) acceptor impurity mixes and begins layer 1002.

In the present embodiment, increase Al by ladder ground _xGa _1-xAl in N (0.01≤x≤0.13) the acceptor impurity doping beginning layer 1002 forms, and the dopant profiles of Mg is risen more precipitously.

And, in the present embodiment, owing to can suppress to result from the generation of the lattice deformability of lattice constant difference, so, the stress that can reduce on the active coating to be applied in, and realize reducing because of can be with the generation of the discontinuous grade that causes (notch).

And,, so improved injection efficiency, further reduce threshold current and improve reliability, thereby realize the raising of rate of finished products to the hole of active coating owing to can reduce the influence of the piezoelectric field effect that produces because of compression stress effectively.

In the present embodiment, though form from 0.01 by every 1nm ladder ground rising 0.03 with Al and to have formed the thick Al of 5nm up to 0.13 mode _xGa _1-xN (0.01≤x≤0.13) acceptor impurity mixes and begins layer 1002, but resulting thus effect is not only can obtain when Al composition ladder ground is increased.As amplify shown in the part of Figure 11 (b), form or increase by increasing Al continuously in the parabola mode, also can reduce the generation of the distortion that causes by the lattice constant difference significantly, can suppress fully by can be with the generation of the discontinuous grade that causes.

As mentioned above, according to nitride semiconductor device of the present invention, owing to can improve the efficient of charge carrier sealing, so do not need to pay attention to by the sealing that plays the charge carrier of realizing as the 3rd p type nitride semiconductor layer of the function of coating layer by the 2nd p type nitride semiconductor layer.Therefore, allow that the band gap with coating layer (the 3rd p type nitride semiconductor layer) diminishes, its result, the Al that can reduce in the coating layer forms.In the execution mode of following explanation, by comparing, reduce the Al ratio of components of coating layer (the 3rd p type nitride semiconductor layer) with above-mentioned each execution mode, its band gap is set at littler than the band gap of a p type nitride semiconductor layer.Owing to play reduction, the series resistance Rs of nitride semiconductor device is reduced, so can reduce consumed power as the Al ratio of components in the 3rd p type nitride semiconductor layer of the function of coating layer.

(execution mode 8)

Below, the 8th execution mode of nitride semiconductor device of the present invention is described with reference to Figure 12.

At first, prepare n-GaN substrate 1601, after cleaning its surface, substrate 1601 is arranged on the pedestal in the growth furnace by organic solvent and acid.Use N ₂Gas is warmed up to 1000 ℃ with 1 ℃/second heating rate after fully replacing in growth furnace, carrier gas is being switched to H ₂In the time of gas, beginning ammonia (NH ₃) supply carry out the cleaning of substrate surface.The time of this cleaning is preferably carried out more than 1 minute.Afterwards, begin to supply with trimethyl gallium (TMG) and monosilane (SiH ₄), carry out the growth of the thick n-GaN layer 1602 of 2 μ m, then, add trimethylaluminum (TMA), carry out the thick n-Al of 1.5 μ m _0.05Ga _0.95The growth of N coating layer 1603.Then, after the n-GaN light guide layer 1604 of the supply that stops TMA and the 0.1 μ m that grown, carrier gas is become N ₂, stop NH ₃Supply, and growth temperature cooled to 780 ℃.

Then, by supplying with NH ₃, TMG and front three indium (TMI), and will be on light guide layer 1604 In of the about 3nm of growth thickness _0.1Ga _0.9N trap layer and on the trap layer In of the about 7nm of growth thickness _0.02Ga _0.98The N barrier layer is during as 1 cycle, and the semiconductor layer in 3 cycles of growing forms multiple quantum trap (MQW) active coating 1605 thus.

Then, at the thick non-In that mixes that oozes of 30nm that grown _0.02Ga _0.98The N intermediate layer 1606 and thick non-the oozing after the assorted GaN intermediate layer 1607 of 30nm of having grown stop the supply of TMG.Supplying with N ₂And NH ₃State under be warmed up to 1000 ℃ rapidly, and carrier gas is switched to N ₂And H ₂Mist.Restart the supply of TMG and TMA, the p-Al that the 45nm that grows is thick _0.10Ga _0.90N intermediate layer (doping enhancement layer) 1608.

When this doping enhancement layer 1608 begins to grow or in the growth way, close magnesium (Cp by dicyclopentadiene ₂Mg) beginning Mg mixes.

Doping enhancement layer 1608 begins after the growth, in its growth way, under the situation that has begun the Mg doping, can form the Al that does not have doped with Mg on doping enhancement layer 1608 _0.10Ga _0.90The Al of the N underclad portion and the Mg that mixed _0.10Ga _0.90The N top section.In other words, doping enhancement layer 1608 becomes to have and comprises the non-assorted Al that oozes _0.10Ga _0.90N underclad portion and Mg doped with Al _0.10Ga _0.90Both structure of N top section.In this case, the non-Al that mixes that oozes _0.10Ga _0.90The N underclad portion is corresponding to the Al in the execution mode 1 _0.03Ga _0.97N intermediate layer 408, the Mg doped with Al _0.10Ga _0.90The N top section is equivalent to the p-Al in the execution mode 1 _0.03Ga _0.97The N acceptor impurity mixes and begins layer 409.

In addition,, postpone, also can form the non-assorted Al that oozes owing to mix even when beginning to grow, begin under the situation of Mg doping with doping enhancement layer 1608 _0.10Ga _0.90The N underclad portion.

Like this, though on the part of doping enhancement layer 1608, can form the zone of the Mg that undopes,, because the thermal diffusion of the Mg that produces in operation thereafter, Mg also can be entrained on doping enhancement layer 1608 all.

In addition, in doping enhancement layer 1608, the part of the Mg that mixed plays the function as the present invention's the one p type nitride semiconductor layer.

After having formed doping enhancement layer 1608, the thick p-Al of 10nm has grown _0.16Ga _0.84The N electronics overflows and suppresses layer 1609.This p-Al _0.16Ga _0.84The N electronics overflows and suppresses layer 1609 function that plays as the present invention's the 2nd p type nitride semiconductor layer.

At the p-Al that grown _0.16Ga _0.84The N electronics overflows and suppresses promptly carrier gas to be switched to H after the layer 1609 ₂, at the p-Al that grown _0.03Ga _0.97After the N coating layer 1610, the p-GaN contact layer 11611 that stacked above one another 50nm is thick.

In the present embodiment, though used magnesium (Mg), on the basis of Mg, can also add carbon (C), zinc (Zn), beryllium (Be), cadmium p type dopants such as (Cd) as p type dopant.

In addition, nitride semiconductor growth method is not limited to the MOVPE method, can adopt hydride vapor growth method (HVPE method) and molecular beam epitaxy (MBE method) etc., is used to make all methods that proposed so far of compound semiconductor crystal growth.

In the present embodiment, though use TMG as the raw material of Ga, TMA as the raw material of Al, TMI raw material, Cp as In ₂Mg is as raw material and the NH of Mg ₃As the raw material of N, still, if effectively utilize the crystal growth of the principle of above-mentioned condition, unstrpped gas is not limited to these.Also can be with triethyl-gallium (TEG) or gallium chloride (GaCl or GaCl ₃) be used as the raw material of Ga, with triethyl aluminum (TEA) or dimethyl hydrogenation aluminium (DMAH), dimethylaluminum chloride (DMACl) raw material,, two ethyl cyclopentadiene are closed magnesium (EtCp with the raw material of triethylindium (TEI) as In as Al ₂Mg) or two methyl cyclopentadiene close magnesium (EeCp ₂Mg) as the Mg raw material, and with hydrazine (N ₂H ₄) or monomethyl hydrazine (MMH), dimethylhydrazine (DMH) be used as the raw material of N.

In the present embodiment, though in each coating layer and contact layer, used bulk crystals,, also can use superlattice structure.

Then, by utilizing etching will become the p-Al that is partially etched to that resonator forms the zone _0.10Ga _0.90N intermediate layer (doping enhancement layer) 1608 is processed into band shape, and protrusion is formed at the top that forms the zone at resonator.Tape width in the protrusion is about 2～3 μ m.Resonator by the band shape in the mask epitaxial loayer forms the zone, and the part of n type contact layer 1602 is carried out etching till this epitaxial loayer exposes.

Then, respectively the contact portion of mask and p type contact layer overlying electrode and with the contact portion of n type contact layer overlying electrode, by the CVD method etc., in the accumulation of protrusion both sides by silica (SiO ₂) the protection dielectric film 1613 that constitutes, form the current injection area territory.On the p-GaN of dielectric film peristome contact layer 1611 surfaces, form p electrode 1612, on n-GaN contact layer 1602 surfaces, form n electrode 1614.In order to reduce the contact resistance with p electrode 1612, the Mg concentration of p-GaN contact layer 1611 is set at from 1 * 10 ²⁰Cm ^-3To 5 * 10 ²⁰Cm ^-3Like this, made nitride semi-conductor laser shown in Figure 12.

In addition, in the present embodiment, though above the electrode of n side is formed on (with p lateral electrode same side),, also the n electrode can be formed on the back side of n-GaN substrate, constitute from the structure of conducting up and down.

For the semiconductor laser of such acquisition, if apply voltage between p lateral electrode 1612 and n lateral electrode 1614, then the hole can be injected to MQW active coating 1605 from p lateral electrode 1612, and simultaneously, electronics injects from n lateral electrode 1614.Thus, in MQW active coating 1605, the compound again optical gain that produced by between hole and the electronics can cause the laser generation of about 410nm wavelength thus.

Below, illustrate and adopt p-Al _0.10Ga _0.90The Al ratio of components (band gap) in N intermediate layer (doping enhancement layer) 1608 compares p-Al _0.16Ga _0.84N overflow suppress layer 1609 little, compare p-Al _0.03Ga _0.97The validity of the structure that N coating layer 1610 is big.

Figure 13 is near the schematic diagram that constitutes the active coating in the expression present embodiment.From the active coating side, it is formed by the above layer in thickness 3 zones different with Al ratio of components (band gap).

In the present embodiment, the part that is doped Mg in the p-AlGaN doping enhancement layer 1102 is corresponding to a p type nitride semiconductor layer.And p-AlGaN overflows and suppresses layer 1103 corresponding to the 2nd p type nitride semiconductor layer, and p-AlGaN coating layer 1104 is corresponding to the 3rd p type nitride semiconductor layer.Set the Al ratio of components of a p type nitride semiconductor layer for ratio of components height, and the Al ratio of components of the 2nd p type nitride semiconductor layer is constituted height than the 3rd p type nitride semiconductor layer than the 3rd p type nitride semiconductor layer.Its result for band gap, satisfies the relation of the 2nd a p type nitride semiconductor layer＞p type nitride semiconductor layer＞the 3rd p type nitride semiconductor layer.

In its band gap became than the little scope of the 2nd p type nitride semiconductor layer, the Al ratio of components in the p type nitride semiconductor layer preferably used high Al ratio of components as far as possible.By there being a p type nitride semiconductor layer, the doping that can eliminate p type impurity postpones, and can guarantee enough impurity concentrations by relative the 2nd p type nitride semiconductor layer.

Preferred Al ratio of components is: a p type nitride semiconductor layer is that the 5～20%, the 2nd p type nitride semiconductor layer is that the 10～30%, the 3rd p type nitride semiconductor layer is average 3～9%.Best Al ratio of components is: a p type nitride semiconductor layer is that the 6～12%, the 2nd p type nitride semiconductor layer is that the 15～20%, the 3rd p type nitride semiconductor layer is average 3.5～5.5%.Thicken under the situation of formation at layer a p type nitride semiconductor layer and the so-called high Al ratio of components of the 2nd p type nitride semiconductor layer, owing to cause the increase of series resistance, thus compare with the 3rd p type nitride semiconductor layer, need be with the thickness attenuation.Therefore, the preferred thickness of each layer is: a p type nitride semiconductor layer is 1～50nm, and the 2nd p type nitride semiconductor layer is 5～20nm.Best thickness is: a p type nitride semiconductor layer is 5～20nm, and the 2nd p type nitride semiconductor layer is 5～10nm.

In addition, as long as the Al ratio of components of a p type nitride semiconductor layer just can have inclination in the scope of above-mentioned preferred Al ratio of components.And this inclination can be continuous, also can be interim.

And,, then can not be that piece layer but superlattice layer also can if each zone is in the scope of above-mentioned preferred Al ratio of components and thickness.In addition, piece layer and superlattice layer can also be mixed.

According to present embodiment, confirmed by experiment to overflow and suppressed to realize that the concentration of Mg reaches 9 * 10 in the layer 1103 at AlGaN ¹⁸Cm ^-3Above high concentration.

In the present embodiment, though when the growth of doping enhancement layer 1102 begins or in the growth way, begin to mix, but, also can in the whole or part of doping enhancement layer 1102, carry out the doping of Mg, need in doping enhancement layer 1102, the concentration of Mg not uniform.

Overflowing the p type impurity concentration that suppresses in the layer 1103 preferably is in maximum from 8 * 10 ¹⁸Cm ^-3To 2 * 10 ¹⁹Cm ^-3Scope in, and preferred being distributed on the thickness direction of impurity concentration also is uniform.

Like this, owing to can suppress the influence that Mg mixes and postpones, so the Mg concentration that the AlGaN of band-gap energy maximum in the laser structure is overflowed suppress in the layer 1103 and the Mg concentration of coating layer are almost equal by inserting AlGaN doping enhancement layer 1102.Like this, by improving the hole injection efficiency, can be when reducing threshold current, suppress the rising of the operating voltage that the dislocation because of the pn interface location causes etc.Particularly, identical by doping enhancement layer 1102 is formed superlattice layer even average A l forms, also can form the high part of Al concentration, thereby can improve the abruptness that Mg is taken into.

In addition, owing to suppress layer 1103 and constitute, can reduce the activation energy that Mg is led, so can reduce series resistance by superlattice layer by making to overflow.This effect also can replace Ga, by comprising the p-Al of In _0.90In _0.10N acceptor impurity doping beginning layer obtains, as long as comprise Al at least in the layer that begins to mix.

By this structural research, if suppress layer for overflowing, the doped p type dopant then can fully be locked in charge carrier in this layer fully.Thus, almost do not have to consider the necessity of sealing charge carrier in coating layer, make it possible to reduce the Al ratio of components of AlGaN coating layer 1104.And, for the sealing of light,, also can compensate by the thickness that thickens coating layer even reduce the Al ratio of components of coating layer.

According to the above description, control p type concentration of dopant, can improve the sealing of charge carrier, and can realize low resistanceization based on the reduction of coating layer Al ratio of components by utilizing structural research.Thus, can reduce device series resistance and can reduce operating voltage.

Though the laser structure on the GaN substrate has been described in the present embodiment, if but crystal growth of the present invention is the crystal growth that has effectively utilized the principle of above-mentioned condition, then to be not limited to be GaN to substrate, can also be nitride-based semiconductor bulk (bulk) substrate, sapphire substrate and silicon carbide substrates such as AlGaN, InGaN and AlGaInN, silicon substrate, on gallium arsyl plate Grown GaN etc., use the growth of selectivity transverse direction and the ELO-GaN substrate made.

And, though laser component has been described in the present embodiment, be not limited to this, can also be applied to light-emitting diode.And, the pn knot can be applied to have, and all elements with low resistanceization of overflowing of electronics need be prevented.And then above-mentioned effect is also set up on BAlGaInN is all with the mixed crystal compound semiconductor that contains arsenic (As), phosphorus (P).

(execution mode 9)

With reference to Figure 14, the 9th execution mode of nitride semiconductor device of the present invention is described.

At first, after the surface of n-GaN substrate 1701 cleaned by organic solvent and acid, substrate 1701 is arranged on the pedestal (suscepter) in the growth furnace.Pass through N ₂After in growth furnace, replacing fully, be warmed up to 1000 ℃, carrier gas is being switched to H with 1 ℃/second heating rate ₂The time, begin to supply with ammonia (NH ₃) carry out the cleaning (cleaning) of substrate surface.The time of preferred this cleaning carried out more than 1 minute.Then, begin to supply with trimethyl gallium (TMG) and monosilane (SiH ₄), the thick n-GaN layer 1702 of 2 μ m of growing then, adds trimethylaluminum (TMA), and the thick n-Al of 1.5 μ m grows _0.05Ga _0.95N coating layer 1703.Make in the supply that stops TMA after n-GaN light guide layer 1704 grows into 0.1 μ m, carrier gas is become N ₂And stop NH ₃Supply, and growth temperature is reduced to 780 ℃.

Then, by supplying with NH ₃, TMG and front three indium (TMI), and will on light guide layer 1704, be the In of about 3nm by growth thickness _0.1Ga _0.9N trap layer and on the trap layer growth thickness be the In of about 7nm _0.02Ga _0.98The N barrier layer forms multiple quantum trap (MQW) active coating 1705 by the semiconductor layer that formed for 3 cycles during as 1 cycle.

Then, at the thick non-In that mixes that oozes of 30nm that grown _0.02Ga _0.98Non-the oozing after the assorted GaN intermediate layer 1707 that N intermediate layer 1706 and 30nm are thick stops the supply of TMG.Supplying with N ₂And NH ₃State under be warmed up to 1000 ℃ rapidly, and carrier gas is switched to N ₂And H ₂Mist.Restart the supply of TMG and TMA, TMI, the p-Al that the 45nm that grows is thick _0.10Ga _0.85In _0.05N intermediate layer (doping enhancement layer) 1708.In the growth way in this intermediate layer, close magnesium (Cp by dicyclopentadiene ₂Mg) beginning Mg mixes.Then, at the thick p-Al of 10nm that grown _0.16Ga _0.75In _0.10N overflows and suppresses promptly carrier gas to be switched to H after the layer 1709 ₂, come stacked above one another p-Al _0.03Ga _0.97The p-GaN contact layer 1711 that N coating layer 1710 and 50nm are thick.

According to said method, can obtain to constitute the epitaxial loayer of semiconductor laser.In addition, because the production process of nitride semi-conductor laser after this is identical with execution mode 8, therefore omit its explanation.

In addition, in the present embodiment,, its replacement can also be used carbon (C), zinc (Zn), beryllium (Be), cadmium (Cd) etc. though used magnesium (Mg) as p type dopant.

And, though use the MOVPE method in the present embodiment as nitride semiconductor growth method, but be not limited to this, can also adopt hydride vapor growth method (HVPE method) and molecular beam epitaxy (MBE method) etc. to be used for all methods that proposed so far of growth compound semiconductor crystal.

And, though in the present embodiment, use TMG as the raw material of Ga, TMA as the raw material of Al, TMI raw material, Cp as In ₂Mg is as raw material and the NH of Mg ₃As the raw material of N, still, if effectively utilize the crystal growth of the principle of above-mentioned condition, then unstrpped gas is not limited to these.Also can be with triethyl-gallium (TEG) or gallium chloride (GaCl or GaCl ₃) be used as the raw material of Ga, with triethyl aluminum (TEA) or dimethyl hydrogenation aluminium (DMAH), dimethylaluminum chloride (DMACl) raw material,, two ethyl cyclopentadiene are closed magnesium (EtCp with the raw material of triethylindium (TEI) as In as Al ₂Mg) or two methyl cyclopentadiene close magnesium (EeCp ₂Mg) as the Mg raw material, and with hydrazine (N ₂H ₄) or monomethyl hydrazine (MMH), dimethylhydrazine (DMH) be used as the raw material of N.

And, in the present embodiment, though bulk crystals is used on each coating layer and contact layer,, also can use superlattice structure.

Below, p-Al is described _0.10Ga _0.85In _0.05The Al in N intermediate layer (doping enhancement layer) 1708 forms (band gap) employing and compares p-Al _0.16Ga _0.75In _0.10N overflow suppress layer 1709 little, compare p-Al _0.03Ga _0.97The structure that N coating layer 1710 is big, and at p-Al _0.16Ga _0.75In _0.10N overflows and suppresses layer 1709 and p-Al _0.10Ga _0.85In _0.05Comprise the validity that In forms on the N intermediate layer 1708.

The architectural feature that present embodiment is used is: with p-Al _0.10Ga _0.85In _0.05The higher layer of the Al ratio of components in N intermediate layer (doping enhancement layer) 1708 and so on is inserted in the AlGaInN electronics and overflows before the inhibition layer, and the doping that makes Mg is from p-Al _0.10Ga _0.85In _0.05The N intermediate layer forms middle beginning.As implement in the mode 8 explanation, (for example Mg etc.) enters in the alloy semiconductor layer that comprises Al easily because p type impurity, so have the significant feature that is difficult to mix and postpones and so on.And, because depending on Al, the easy degree that p type impurity enters forms, be between 0% to 50% therefore at the Al ratio of components, and along with the increase of Al ratio of components, the amount that p type impurity enters also increases.

In the present embodiment, different with execution mode 8, near the big AlGaN of lattice constant difference between configuration and the InGaN in statu quo not active coating, but in order to suppress the lattice constant official post AlGaInN that comprises In.By adopting this structure, can mix by high Al composition inhibition recently on one side postpones, Yi Bian eliminate inhomogeneous that the trap layer of formation active coating is out of shape by reducing the lattice constant difference as much as possible, thus influence suppressed to the characteristics of luminescence.

Figure 15 is near the schematic diagram that constitutes the active coating in the expression present embodiment.From the active coating side, form by thickness, Al ratio of components (band gap) the above layer in 3 zones different with the In ratio of components.In the present embodiment, p-AlGaInN doping enhancement layer 1803 is corresponding to a p type nitride semiconductor layer, p-AlGaInN overflows and suppresses layer 1804 corresponding to the 2nd p type nitride semiconductor layer, and p-AlGaInN coating layer 1805 is corresponding to the 3rd p type nitride semiconductor layer.The Al ratio of components (band gap) of the one p type nitride semiconductor layer constitutes little than the 2nd p type nitride semiconductor layer, and big than the 3rd p type nitride semiconductor layer.Its band gap than the little scope of the 2nd p type nitride semiconductor layer in, the Al ratio of components in the preferred p type nitride semiconductor layer uses high Al ratio of components as far as possible.On this basis, form by in the 2nd a p type nitride semiconductor layer and a described p type nitride semiconductor layer, comprising In, can suppress and near the active coating of existence between lattice constant poor.Based on the existence of a p type nitride semiconductor layer, the doping that can eliminate the p type impurity that takes place in prior art constitutes postpones, and can guarantee enough impurity concentrations with respect to the 2nd p type nitride semiconductor layer.

In addition, preferred Al ratio of components is: a p type nitride semiconductor layer is that the 5～20%, the 2nd p type nitride semiconductor layer is that the 10～30%, the 3rd p type nitride semiconductor layer is average 3～9%.Best Al ratio of components is: a p type nitride semiconductor layer is that the 6～12%, the 2nd p type nitride semiconductor layer is that the 15～20%, the 3rd p type nitride semiconductor layer is average 3.5～5.5%.And preferred In ratio of components is: a p type nitride semiconductor layer is that the 1～20%, the 2nd p type nitride semiconductor layer is 1～30%.The Al that like this, preferably the In ratio of components is set at least than each layer forms little.

In the present embodiment, owing to compare with the Al ratio of components in the p type nitride semiconductor layer, Al ratio of components in the 2nd p type nitride semiconductor layer is set highly, so relate to the In ratio of components, also is set at ratio the one p type nitride semiconductor layer big of the 2nd p type nitride semiconductor layer.Thus, can reduce the poor of each layer crystal lattice constant, thereby reduce the distortion of active coating.But, under the closer situation of the distance of a p type nitride semiconductor layer and active coating, also there is following situation, promptly, compare with the 2nd p type nitride semiconductor layer that the Al ratio of components is big, the lattice constant of a p type nitride semiconductor layer is subjected to bigger influence sometimes with respect to the distortion of active coating.In this case, as shown in Figure 16, preferably In is formed and be set at: compare the 2nd p type nitride semiconductor layer (p-AlGaInN overflows and suppresses layer 1904) little with a p type nitride semiconductor layer (p-AlGaInN doping enhancement layer 1903).

And if owing to the layer that thickens the high Al ratio of components of a p type nitride semiconductor layer and the 2nd p type nitride semiconductor layer what is called, then series resistance can increase, so the thickness of these layers need be littler than the 3rd p type nitride semiconductor layer.Therefore, the preferred thickness of each layer is: a p type nitride semiconductor layer is 1～50nm, and the 2nd p type nitride semiconductor layer is 5～20nm.Best thickness is: a p type nitride semiconductor layer is 5～20nm, and the 2nd p type nitride semiconductor layer is 5～10nm.

In addition, if the Al ratio of components of a p type nitride semiconductor layer and In ratio of components are in the scope of above-mentioned preferred Al ratio of components and In composition, then also can have inclination.And this inclination can be continuous, also can be interim.And, if each zone is in the scope of above-mentioned preferred Al ratio of components and In ratio of components and thickness, then can not piece layer but superlattice layer, also can be piece layer and superlattice layer mix.

By adopting the structure of present embodiment, though the AlGaInN electronics overflow suppress layer 1804 and p-AlGaInN doping enhancement layer between near interface, also experimental verification Mg concentration be 9 * 10 ¹⁸Cm ^-3Above high concentration.Hence one can see that, and it is peer-level that this value is compared with the Mg concentration that execution mode 8 is enumerated, even recently reducing under the situation of lattice constant difference by the In composition, as long as use high Al ratio of components, just can obtain same doping effect.For the doping starting position, need from the initial or way of doping enhancement layer 1803, carry out.In addition, also can in the whole or part of doping enhancement layer, carry out the doping of impurity, not need that impurity concentration is uniform in the layer.For overflowing the doping content that suppresses layer 1804, it is maximum from 8 * 10 preferably to mix equably ¹⁸Cm ^-3To 2 * 10 ¹⁹Cm ^-3P type impurity.

Like this,, can suppress the influence that Mg mixes and postpones, thereby the Mg concentration of Mg concentration that the AlGaInN electronics of band-gap energy maximum in the laser structure is overflowed suppress in the layer 1804 and coating layer is almost equal by inserting AlGaInN doping enhancement layer 1803.By improving the hole injection efficiency, can reduce threshold current.Particularly, by doping enhancement layer 1803 is made superlattice layer,, also can form the high part of Al concentration, thereby can improve the abruptness that Mg enters even then average A l ratio of components is identical.And, make superlattice layer by overflowing inhibition layer 1804, can reduce the activation energy that Mg is led, reduce series resistance.

By this structural research, suppress layer 1804 for overflowing, if doped p type dopant fully then can fully be locked in charge carrier in this layer.Thus, almost do not have to consider the necessity of sealing charge carrier in coating layer, thereby can reduce the Al ratio of components of AlGaN coating layer 1805.In addition, even reduce the Al ratio of components of coating layer, for light close into, also can remedy by the thickness that thickens coating layer.According to said method, control p type concentration of dopant by utilizing structural research, can improve the sealing of charge carrier, and the reduction of Al ratio of components that can be by coating layer reduces resistance.Thus, can reduce the series resistance of device, reduce operating voltage.

In addition, though the laser structure on the GaN substrate has been described in the present embodiment, if but crystal growth of the present invention is the crystal growth that effectively utilizes the principle of above-mentioned condition, then substrate is not limited to GaN, also can be nitride-based semiconductor bulk (bulk) substrates such as AlGaN, InGaN or AlGaInN, sapphire substrate, silicon carbide substrate, silicon substrate, institute's Grown GaN etc. or use the growth of selectivity transverse direction and the ELO-GaN substrate made on gallium arsyl plate.

And though the semiconductor element in the above-mentioned execution mode all is a laser component, the present invention is not limited to this, can also be applied to have the pn knot, need prevent simultaneously that electronics from overflowing all nitride semiconductor devices with low resistanceization.For example, can be applied to nitride semiconductor devices such as light-emitting diode, light receiving element, transistor.

In aforesaid execution mode,, on the basis of Mg, can also add carbon (C), zinc (Zn), beryllium (Be), cadmium (Cd) etc. though all used magnesium (Mg) as p type acceptor impurity.And, as carrying out the nitride-based semiconductor that Mg mixes, can also be BAlGaInN and the AlGaInNAsP mixed crystal compound semiconductor that contains As, P.

Industrial applicibility

According to the present invention, band-gap energy is bigger than active coating by arranging, band-gap energy overflows than electronics and presses down The p-type acceptor impurity that preparative layer is little mixes and begins layer, can realize not prolonging because storage effect causes mixing Slow precipitous acceptor impurity distributes. Thus, can make and have high reliability low threshold current and low The compound semiconductor light of operating voltage receives transmitting element, and makes its repeatability, has good uniformity.

This nitride semiconductor device of the present invention makes mainly as the light source of CD association area With, also can be applied to laser printer, bar code reader etc.

Claims (17)

1. nitride semiconductor device comprises: p type nitride semiconductor layer, n type nitride semiconductor layer and be clamped in described p type nitride semiconductor layer and described n type nitride semiconductor layer between active coating, wherein,

Described p type nitride semiconductor layer has:

A p type nitride semiconductor layer that comprises Al and Mg; With

The 2nd p type nitride semiconductor layer that comprises Mg,

A described p type nitride semiconductor layer between described active coating and described the 2nd p type nitride semiconductor layer,

Described the 2nd p type nitride semiconductor layer has the big band gap of band gap than a described p type nitride semiconductor layer.

2. nitride semiconductor device according to claim 1 is characterized in that, described the 2nd p type nitride semiconductor layer plays a part the barrier layer of overflowing as the charge carrier that suppresses from described active coating.

3. nitride semiconductor device according to claim 1 is characterized in that, the Al concentration of a described p type nitride semiconductor layer is 1 * 10 ²⁰Cm ^-3More than 2 * 10 ²¹Cm ^-3Below,

Al concentration is 1 * 10 in the described p type nitride semiconductor layer ²⁰Cm ^-3More than 2 * 10 ²¹Cm ^-3The thickness in following zone is more than the 1nm.

4. nitride semiconductor device according to claim 1 is characterized in that, also comprise between a described p type nitride semiconductor layer and described active coating and comprise Al non-ly ooze assorted nitride semiconductor layer.

5. nitride semiconductor device according to claim 4 is characterized in that, describedly non-ly oozes assorted nitride semiconductor layer and has the little band gap of band gap than described the 2nd p type nitride semiconductor layer.

6. nitride semiconductor device according to claim 5 is characterized in that, the described non-nitride semiconductor layer of mixing that oozes has the band gap that equates with the band gap of a described p type nitride semiconductor layer.

7. according to any one described nitride semiconductor device in the claim 4～6, it is characterized in that the described non-aggregate thickness that oozes an assorted nitride semiconductor layer and a described p type nitride semiconductor layer is below the above 50nm of 1nm.

8. nitride semiconductor device according to claim 7 is characterized in that, the thickness of described the 2nd p type nitride semiconductor layer is below the above 20nm of 5nm.

9. nitride semiconductor device according to claim 8 is characterized in that, in described the 2nd p type nitride semiconductor layer, Mg concentration is 8 * 10 ¹⁸Cm ^-3The thickness in following zone is below the 1nm.

10. nitride semiconductor device according to claim 1, it is characterized in that, described p type nitride semiconductor layer also has the 3rd p type nitride semiconductor layer, and described the 3rd p type nitride semiconductor layer has the little band gap of band gap than described the 2nd p type nitride semiconductor layer

Described the 2nd p type nitride semiconductor layer is between described the 3rd a p type nitride semiconductor layer and a described p type nitride semiconductor layer.

11. nitride semiconductor device according to claim 10 is characterized in that, the band gap of described the 3rd p type nitride semiconductor layer is littler than the band gap of a described p type nitride semiconductor layer.

12. nitride semiconductor device according to claim 10 is characterized in that, described the 3rd p type nitride semiconductor layer plays the function of coating layer.

13., it is characterized in that at least one side of a described p type nitride semiconductor layer and described the 2nd p type nitride semiconductor layer comprises In according to any one described nitride semiconductor device in the claim 10～12.

14. nitride semiconductor device according to claim 13 is characterized in that, the In ratio of components of described the 2nd p type nitride semiconductor layer is bigger than the In ratio of components of a described p type nitride semiconductor layer.

15. the manufacture method of a nitride semiconductor device, described nitride semiconductor device comprises: p type nitride semiconductor layer, n type nitride semiconductor layer, and be clamped in active coating between described p type nitride semiconductor layer and the described n type nitride semiconductor layer, described p type nitride semiconductor layer has: a p type nitride semiconductor layer that comprises Al and Mg, the 2nd p type nitride semiconductor layer that comprises Mg, a described p type nitride semiconductor layer is between described active coating and described the 2nd p type nitride semiconductor layer, described the 2nd p type nitride semiconductor layer has the big band gap of band gap than a described p type nitride semiconductor layer, and the manufacture method of described nitride semiconductor device comprises:

Form the operation of described n type nitride semiconductor layer; With

Form the operation of described active coating; With

By supplying with unstrpped gas simultaneously and having the unstrpped gas of Al, form the operation of a described p type nitride semiconductor layer that comprises Al and Mg with Mg; And

The unstrpped gas that has a Mg by supply forms the operation of described the 2nd p type nitride semiconductor layer.

16. manufacture method according to claim 15, it is characterized in that, also comprise: before the operation that forms a described p type nitride semiconductor layer, supply with unstrpped gas, form the non-operation of oozing assorted nitride semiconductor layer that comprises Al with Al by not supplying with p type impurity.

17. according to claim 15 or 16 described manufacture methods, it is characterized in that,

The Al concentration of a described p type nitride semiconductor layer is 1 * 10 ²⁰Cm ^-3More than 2 * 10 ²¹Cm ^-3Below,

In the described p type nitride semiconductor layer, Al concentration is 1 * 10 ²⁰Cm ^-3More than 2 * 10 ²¹Cm ^-3The thickness in following zone is more than the 1nm.

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