CN101593805A - Nitride semiconductor photogenerator - Google Patents

Nitride semiconductor photogenerator Download PDF

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CN101593805A
CN101593805A CNA2009101499745A CN200910149974A CN101593805A CN 101593805 A CN101593805 A CN 101593805A CN A2009101499745 A CNA2009101499745 A CN A2009101499745A CN 200910149974 A CN200910149974 A CN 200910149974A CN 101593805 A CN101593805 A CN 101593805A
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tunnel junction
type nitride
nitride semiconductor
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CN101593805B (en
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驹田聪
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Sharp Corp
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Abstract

The invention discloses a kind of nitride semiconductor photogenerator, described device comprises substrate, and be formed on a n type nitride semiconductor layer on the described substrate, luminescent layer, the one p type nitride semiconductor layer, the 2nd p type nitride semiconductor layer, p type nitride-based semiconductor tunnel junction layer, n type nitride-based semiconductor tunnel junction layer and the 2nd n type nitride semiconductor layer, described p type nitride-based semiconductor tunnel junction layer and described n type nitride-based semiconductor tunnel junction layer have formed tunnel junction, and described p type nitride-based semiconductor tunnel junction layer has the indium content ratio higher than the indium content ratio of described the 2nd p type nitride semiconductor layer.In described p type nitride-based semiconductor tunnel junction layer and the described n type nitride-based semiconductor tunnel junction layer at least one comprises aluminium.

Description

Nitride semiconductor photogenerator
The application is the dividing an application that be on November 22nd, 2007 and denomination of invention the applying date for the Chinese patent application No.200710169305.5 of " nitride semiconductor photogenerator ".
Technical field
The present invention relates to a kind of nitride semiconductor photogenerator, more specifically, relate to a kind of nitride semiconductor photogenerator with tunnel junction.
Background technology
About contain the nitride semiconductor LED device of p type nitride semiconductor layer in its side as light output side, the p lateral electrode that need be formed on usually on the p type nitride semiconductor layer satisfies following three conditions.
First condition is that the p lateral electrode has the high-transmission rate about the light that sends from the nitride semiconductor LED device.Second condition is that the p lateral electrode has resistance and the thickness that allows injection current fully to spread in the plane of luminescent layer.The 3rd condition is that the p lateral electrode has the low contact resistance that is relevant to p type nitride semiconductor layer.
Side at the p of nitride semiconductor LED device type nitride semiconductor layer is under the situation of light output side, be formed on the normally translucent metal electrode of p lateral electrode on the p type nitride semiconductor layer, the thickness that this metal electrode forms such as palladium or nickel is the metal film of approximately several nm to 10nm and is formed on the whole surface of p type nitride semiconductor layer.Yet, such semi-transparent metals electrode has about 50% low transmissivity about the light that sends from the nitride semiconductor LED device, and reduced light output efficiency thus, cause being difficult to obtain the problem of high-brightness nitride semiconductor light emitting diode device.
Therefore, replacement is with such as the film formed semi-transparent metals electrode of the metal of palladium or nickel, made high-brightness nitride semiconductor light emitting diode device with nesa coating, described nesa coating is made and is formed on the whole surface of p type nitride semiconductor layer by ITO (tin indium oxide), thereby has improved light output efficiency.About wherein being formed with the nitride semiconductor LED device of such nesa coating, wait the problem of improving the contact resistance between nesa coating and the p type nitride semiconductor layer by heat treatment.
Patent document 1 (TOHKEMY communique No.2002-319703) discloses a kind of nitride semiconductor LED device with the III group-III nitride semiconductor sandwich construction that is formed on the substrate, and described sandwich construction contains a n type III group-III nitride semiconductor sandwich construction, p type III group-III nitride semiconductor sandwich construction and the 2nd n type III nitride semiconductor layer stack structure at least.N type III nitride semiconductor layer in a n type III group-III nitride semiconductor sandwich construction is provided with negative electrode, n type III nitride semiconductor layer in the 2nd n type III group-III nitride semiconductor sandwich construction is provided with positive electrode, and has formed tunnel junction by n type III nitride semiconductor layer in the 2nd n type III group-III nitride semiconductor sandwich construction and the p type III nitride semiconductor layer in the p type III group-III nitride semiconductor sandwich construction.
In patent document 1 in the disclosed nitride semiconductor LED device, positive electrode is formed on the n type III nitride semiconductor layer place in the 2nd n type III group-III nitride semiconductor sandwich construction, and compare with p type III group-III nitride semiconductor, n type III group-III nitride semiconductor has the carrier density that is easy to increase.Therefore, the conventional structure that is formed on p type III nitride semiconductor layer place with its positive electrode is compared, and can reduce contact resistance, and driving voltage reduces, and can realize that bigger output drives.In addition, owing to reduced the heating of the positive electrode of one of failure factor as the nitride semiconductor LED device, so can think that this diode component can have the reliability of improvement.
Summary of the invention
Yet the nesa coating of being made by ITO has the problem that optical characteristics at high temperature irreversibly changes, and has caused the transmissivity that reduces about visible light.In addition, under the situation of using the nesa coating of making by ITO, because will prevent to reduce, so there is the limited problem of temperature range that forms the nesa coating technology of making by ITO afterwards about visible light transmittance.In addition, exist the nesa coating made by ITO because of the big current practice deterioration problem of blackening thus also.
About disclosed nitride semiconductor LED device in the example of patent document 1, p type InGaN layer and n type InGaN layer that its In (indium) content ratio is substantially equal to the In content ratio of luminescent layer have formed tunnel junction, and corresponding film thickness is each 50nm.
As disclosed in the example of patent document 1, supply In fully for form with solid phase, be necessary growth temperature is reduced to about 800 ℃.Yet, be difficult at low temperatures obtain having 1 * 10 19/ cm 3Or the p type InGaN layer of higher high carrier density.Therefore, can not reduce the loss of voltage at tunnel junction place, the problem that has caused driving voltage to increase.
In addition,, can be reduced, yet because the reliability due to the tunnel junction place loss of voltage is to need the problem paid close attention to the contact resistance of positive electrode about disclosed nitride semiconductor LED device in the patent document 1.
For example, in the example 1 of patent document 1, disclose that to have carrier density be 1 * 10 19/ cm 3P type In 0.16Ga 0.84N layer and carrier density are 1 * 10 20/ cm 3N type In 0.16Ga 0.84The nitride semiconductor LED device of the tunnel junction of N layer.Under the situation of the nitride semiconductor LED device that drives structure like this with high current density, because the high density impurity of the nitride semiconductor layer of InGaN and lattice defect etc. have caused deterioration, this is the reason of reliability deterioration.
Therefore, an object of the present invention is to provide a kind of nitride semiconductor photogenerator that can reduce its driving voltage.
Another object of the present invention provides a kind of nitride semiconductor photogenerator that can improve its reliability.
According to a first aspect of the invention, a kind of nitride semiconductor photogenerator is provided, described device comprises substrate, and be formed on a n type nitride semiconductor layer on the described substrate, luminescent layer, the one p type nitride semiconductor layer, the 2nd p type nitride semiconductor layer, p type nitride-based semiconductor tunnel junction layer, n type nitride-based semiconductor tunnel junction layer and the 2nd n type nitride semiconductor layer, described p type nitride-based semiconductor tunnel junction layer and described n type nitride-based semiconductor tunnel junction layer have formed tunnel junction, and described p type nitride-based semiconductor tunnel junction layer has the indium content ratio higher than the indium content ratio of described the 2nd p type nitride semiconductor layer.
Herein, about the nitride semiconductor photogenerator in the first aspect present invention, " the indium content ratio " in " described p type nitride-based semiconductor tunnel junction layer has the indium content ratio " means the number and the total atom number purpose ratio that is included in the III family element (Al, Ga and In) in the p type nitride-based semiconductor tunnel junction layer of In atom." the In content ratio of the 2nd p type nitride semiconductor layer " means the number and the total atom number purpose ratio that is included in the III family element (Al, Ga and In) in the 2nd p type nitride semiconductor layer of In atom.Here, Al represents aluminium, and Ga represents gallium, and In represents indium.
About the nitride semiconductor photogenerator in the first aspect present invention, preferred the 2nd p type nitride semiconductor layer has the thickness that is not less than 2nm.
About the nitride semiconductor photogenerator in the first aspect present invention, preferred the 2nd p type nitride semiconductor layer has the thickness that is not less than critical thickness.
About the nitride semiconductor photogenerator in the first aspect present invention, preferred the 2nd p type nitride semiconductor layer is doped with doping density and is not less than 1 * 10 19/ cm 3P type impurity.
About the nitride semiconductor photogenerator in the first aspect present invention, preferred described p type nitride-based semiconductor tunnel junction layer has the thickness that is not more than 5nm.
About the nitride semiconductor photogenerator in the first aspect present invention, preferred described p type nitride-based semiconductor tunnel junction layer is doped with doping density and is not less than 1 * 10 19/ cm 3P type impurity.
About the nitride semiconductor photogenerator in the first aspect present invention, the band gap of a preferred described p type nitride semiconductor layer is greater than the band gap of described the 2nd p type nitride semiconductor layer, and the band gap of described the 2nd p type nitride-based semiconductor is greater than the band gap of described p type nitride-based semiconductor tunnel junction layer.
About the nitride semiconductor photogenerator in the first aspect present invention, preferred described n type nitride-based semiconductor tunnel junction layer comprises indium.
About the nitride semiconductor photogenerator in the first aspect present invention, preferred described n type nitride-based semiconductor tunnel junction layer is doped with doping density and is not less than 1 * 10 19/ cm 3N type impurity.
About the nitride semiconductor photogenerator in the first aspect present invention, preferred described n type nitride-based semiconductor tunnel junction layer has the thickness that is not more than 10nm.
According to a second aspect of the invention, a kind of nitride semiconductor photogenerator is provided, described device comprises substrate, and be formed on a n type nitride semiconductor layer on the described substrate in succession, luminescent layer, p type nitride semiconductor layer, p type nitride-based semiconductor tunnel junction layer, n type nitride-based semiconductor tunnel junction layer and the 2nd n type nitride semiconductor layer, described p type nitride-based semiconductor tunnel junction layer and described n type nitride-based semiconductor tunnel junction layer have formed tunnel junction, and in described p type nitride-based semiconductor tunnel junction layer and the described n type nitride-based semiconductor tunnel junction layer at least one comprises aluminium.
Herein, about the nitride semiconductor photogenerator in the second aspect present invention, can the part between the part between part, a described n type nitride semiconductor layer and the described luminescent layer between a described substrate and a described n type nitride semiconductor layer, described luminescent layer and the described p type nitride-based semiconductor tunnel junction layer, and described n type nitride-based semiconductor tunnel junction layer and described the 2nd n type nitride semiconductor layer between the group that constitutes of part form another layer at least one part of choosing.
About the nitride semiconductor photogenerator in the second aspect present invention, the aluminium content of at least one in preferred described p type nitride-based semiconductor tunnel junction layer and the described n type nitride-based semiconductor tunnel junction layer is for being not less than 1 atomic percent and being not more than 5 atomic percents.
About the nitride semiconductor photogenerator in the second aspect present invention, " atomic percent " of expression Al content refers at Al and is included in the p type nitride-based semiconductor tunnel junction layer and is not included under the situation in the n type nitride-based semiconductor tunnel junction layer, and included Al atom number is with respect to the total atom number purpose ratio (%) that is included in the III family element (Al, Ga and In) in the p type nitride-based semiconductor tunnel junction layer.Be included in the n type nitride-based semiconductor tunnel junction layer and be not included under the situation in the p type nitride-based semiconductor tunnel junction layer at Al, " atomic percent " of expression Al content refers to included Al atom number with respect to the total atom number purpose ratio (%) that is included in the III family element (Al, Ga and In) in the n type nitride-based semiconductor tunnel junction layer.Under Al was included in situation in n type nitride-based semiconductor tunnel junction layer and the p type nitride-based semiconductor tunnel junction layer, " atomic percent " of expression Al content referred to included Al atom number with respect to the total atom number purpose ratio (%) that is included in the III family element (Al, Ga and In) in the p type nitride-based semiconductor tunnel junction layer and included Al atom number with respect in the total atom number purpose ratio (%) that is included in the III family element (Al, Ga and In) in the n type nitride-based semiconductor tunnel junction layer at least one.
About the nitride semiconductor photogenerator in the second aspect present invention, preferred described p type nitride-based semiconductor tunnel junction layer comprises aluminium and indium, and indium content is higher than aluminium content.
About the nitride semiconductor photogenerator in the second aspect present invention, preferred described n type nitride-based semiconductor tunnel junction layer comprises aluminium and indium, and indium content is higher than aluminium content.
About the nitride semiconductor photogenerator in the second aspect present invention, preferred described p type nitride-based semiconductor tunnel junction layer is doped with doping density and is not less than 1 * 10 19/ cm 3P type impurity.
About the nitride semiconductor photogenerator in the second aspect present invention, preferred described n type nitride-based semiconductor tunnel junction layer is doped with doping density and is not less than 1 * 10 19/ cm 3N type impurity.
About the nitride semiconductor photogenerator in the first aspect present invention, preferred described n type nitride-based semiconductor tunnel junction layer has the thickness that is not more than 10nm.
About the present invention, " doping density of p type impurity " refers to the density of the p type foreign atom that is included in the nitride-based semiconductor, " doping density of n type impurity " refers to the density of the n type foreign atom that is included in the nitride-based semiconductor, and in the doping density of the doping density of described p type impurity and described n type impurity each can be come quantitative calculation by for example SIMS (secondary ion mass spectrum).
According to a first aspect of the invention, can provide the nitride semiconductor photogenerator that can reduce driving voltage.
According to a second aspect of the invention, can provide the nitride semiconductor photogenerator that can improve reliability.
For following detailed description the in detail of the present invention, above and other purpose of the present invention, feature, aspect and advantage will become more clear in conjunction with the drawings.
Description of drawings
Fig. 1 is the schematic cross sectional view as the preferred embodiment of the nitride semiconductor LED device of an example of nitride semiconductor photogenerator of the present invention;
Fig. 2 is the schematic cross sectional view of the nitride semiconductor LED device in the example 1 to 2;
Fig. 3 shows the relation between the thickness of nitride semiconductor LED device drive voltage and p type InGaN layer in the example 1;
Fig. 4 shows the relation between the thickness of nitride semiconductor LED device drive voltage and p type tunnel junction layer in the example 2;
Fig. 5 shows the relation between the thickness of the light output of nitride semiconductor LED device in the example 2 and p type tunnel junction layer;
Fig. 6 is the schematic cross sectional view of the nitride semiconductor LED device in the example 3;
Fig. 7 is the schematic cross sectional view of the nitride semiconductor LED device in the comparative example 1;
Fig. 8 is the schematic cross sectional view as the preferred embodiment of the nitride semiconductor LED device of an example of nitride semiconductor photogenerator of the present invention;
Fig. 9 is the schematic cross sectional view of the nitride semiconductor LED device in the example 4 to 6;
Figure 10 shows the relation between the Al content of the breakdown current density of the nitride semiconductor LED device in the example 4 and n type tunnel junction layer and p type tunnel junction layer; And
Figure 11 shows the relation between the Al content of nitride semiconductor LED device drive voltage in the example 4 and n type tunnel junction layer and p type tunnel junction layer.
Embodiment
Below, embodiment of the present invention will be described.In accompanying drawing of the present invention, identical Reference numeral is represented identical or corresponding element.
First embodiment
Fig. 1 shows the schematic cross sectional view as the preferred embodiment of the nitride semiconductor LED device of an example of nitride semiconductor photogenerator of the present invention.Herein, nitride semiconductor LED device configuration shown in Figure 1 is for comprising substrate 1, and be deposited on a n type nitride semiconductor layer 2 on the substrate 1 in succession, luminescent layer 3, the one p type nitride semiconductor layer 4, the 2nd p type nitride semiconductor layer 5, p type nitride-based semiconductor tunnel junction layer 6, n type nitride-based semiconductor tunnel junction layer 7, the evaporation of n type nitride-based semiconductor reduces layer (n-type nitride semiconductorvaporization reduction layer) the 8 and the 2nd n type nitride semiconductor layer 9, and has n lateral electrode 10 that is formed on the n type nitride semiconductor layer 2 and the p lateral electrode 11 that is formed on the 2nd n type nitride semiconductor layer 9.
The conventional structure that is formed on conventional p type nitride semiconductor layer place with positive electrode is compared, so the nitride semiconductor photogenerator of structure can have littler contact resistance, also can have the driving voltage that reduces, and the problem that will pay close attention to is how to reduce the loss of voltage at the tunnel junction place, and described tunnel junction is the knot between p type nitride-based semiconductor tunnel junction layer 6 and the n type nitride-based semiconductor tunnel junction layer 7.
Usually the tunnelling probability Tt that represents tunnel junction by following formula (1).
Tt＝exp((-8π(2m e) 1/2Eg 3/2)/(3qhε))...(1)
In above expression formula (1), Tt represents tunnelling probability, m eThe effective mass of expression conduction band electron (conductionelectron), Eg represents energy gap, and q represents the electric charge of electronics, and h represents Planck's constant, and ε represents to be applied to the electric field of tunnel junction.
In order to reduce the driving voltage of nitride semiconductor photogenerator, required is to increase this tunnelling probability Tt.From above expression formula (1) as can be seen, the possible method of increase tunnelling probability Tt is to reduce the energy gap Eg at tunnel junction place and increase the electric field ε that is applied to tunnel junction.
In order to reduce the energy gap Eg at tunnel junction place, preferably p type nitride-based semiconductor tunnel junction layer 6 and n type nitride-based semiconductor tunnel junction layer 7 each all contain In and the In content ratio is higher.If the In content ratio of p type nitride-based semiconductor tunnel junction layer 6 is higher than the In content ratio of luminescent layer 3, then the light that sends of luminescent layer 3 is absorbed by tunnel junction, and this is the reason of light output efficiency deterioration.Therefore, preferably the thickness of p type nitride-based semiconductor tunnel junction layer 6 is less.
N type nitride-based semiconductor tunnel junction layer 7 contains the n type impurity of overactivity ratio (activation ratio) and can realize high carrier density thus.Therefore, the width of depletion layer on the n side of tunnel junction in the time of can reducing to be driven.Improving aspect the light output efficiency, preferably the thickness of n type nitride-based semiconductor tunnel junction layer 7 is equal to or less than the thickness of p type nitride-based semiconductor tunnel junction layer 6.
Yet, as mentioned above, to enter fully at the In of solid phase under the situation of p type nitride-based semiconductor tunnel junction layer 6, growth temperature has to be reduced to about 800 ℃, and is difficult to increase the carrier density of p type nitride-based semiconductor tunnel junction layer 6.
Therefore, the present invention has following feature, that is, the In content ratio in the p type nitride-based semiconductor tunnel junction layer 6 is higher than the In content ratio in the 2nd p type nitride semiconductor layer 5.Because this structure, p type nitride-based semiconductor tunnel junction layer 6 has lattice mismatch with respect to the 2nd p type nitride semiconductor layer 5, and since these layers at the interface or the difference of the electron affinity between near interface the 2nd p type nitride semiconductor layer 5 and the p type nitride-based semiconductor tunnel junction layer 6 produced electric field, therefore, the hole of p type nitride-based semiconductor tunnel junction layer 6 attracted near interface and and produced two-dimensional electron gas.Because the effect of the two-dimensional electron gas that is produced can increase carrier density partly at the near interface of p type nitride-based semiconductor tunnel junction layer 6 one sides.Therefore, can increase the tunnelling probability Tt of tunnel junction.Thereby, can reduce the loss of voltage at tunnel junction place.
In order to increase the electric field ε that is applied to tunnel junction, can increase the corresponding ionized impurities density of p type nitride-based semiconductor tunnel junction layer 6 and n type nitride-based semiconductor tunnel junction layer 7.Herein, since preferably the ionized impurities density of p type nitride-based semiconductor tunnel junction layer 6 be 1 * 10 18/ cm 3Or bigger, so preferably in the p type nitride-based semiconductor tunnel junction layer 6 doping density of p type impurity be 1 * 10 19/ cm 3Or it is bigger.As p type impurity of the present invention, for example can use Mg (magnesium) and/or Zn (zinc) to be used for mixing.
Because preferably the ionized impurities density of n type nitride-based semiconductor tunnel junction layer 7 is 1 * 10 19/ cm 3Or bigger, so preferably in the n type nitride-based semiconductor tunnel junction layer 7 doping density of n type impurity be 1 * 10 19/ cm 3Or it is bigger.As n type impurity of the present invention, for example can use Si (silicon) and/or Ge (germanium) to be used for mixing.
The other method that increases tunnelling probability Tt is to form intermediate level.A method that forms intermediate level for example is to form dislocation.In order to form dislocation, the 2nd p type nitride semiconductor layer 5 preferably has lattice mismatch with respect to a following p type nitride semiconductor layer 4, and preferably have 2nm or bigger thickness, and described thickness is preferably critical thickness or bigger.So forming under the situation of dislocation, dislocation has caused the intermediate level of tunnel junction.Charge carrier also can tunnelling pass through intermediate level, can increase tunnelling probability Tt thus, and might reduce driving voltage.
Critical thickness is represented by following formula (2) usually.
h c＝(a e/(2 1/2πf))×((1-v/4)/(1+v))×(ln(h c2 1/2/a e)+1)...(2)
In expression formula (2), h cThe critical thickness of representing the 2nd p type nitride semiconductor layer 5, a eRepresent the lattice constant of the 2nd p type nitride semiconductor layer 5, f represents (a s-a e)/a eThe maximum of absolute value, v represents the Poisson's ratio of the 2nd p type nitride semiconductor layer 5.In addition, a sThe lattice constant of representing a p type nitride semiconductor layer 4.
As substrate 1, for example can use Sapphire Substrate, silicon substrate, silicon carbide substrates or zinc oxide substrate or the like.
As a p type nitride semiconductor layer 2, for example can use the nitride semiconductor crystal that is doped with n type impurity.
As luminescent layer 3, for example can grow has the nitride semiconductor crystal of single quantum well (SQW) structure or Multiple Quantum Well (MQW) structure.Particularly, preferably use the luminescent layer that contains multi-quantum pit structure, described multi-quantum pit structure comprises the nitride semiconductor crystal of being represented by following composition formula:
Al a1In b1Ga 1-(a1+b1)N(0≤a1≤1，0≤b1≤1，0≤1-(a1+b1)≤1)
In described composition formula, a1 represents the content ratio of Al, and b1 represents the content ratio of In, the content ratio of 1-(a1+b1) expression Ga.
As a p type nitride semiconductor layer 4, can use the nitride semiconductor crystal that is doped with p type impurity.For example, can use the p type nitride semiconductor layer that contains Al of growing p-type GaN layer on it, perhaps growth thereon has further growth on the p type nitride semiconductor layer that contains Al of p type GaN layer to contain the p type nitride semiconductor layer of In.
As the 2nd p type nitride semiconductor layer 5, can use the nitride semiconductor crystal that is doped with p type impurity.The superiors with respect to a p type nitride semiconductor layer 4 have under the situation of lattice mismatch at the 2nd p type nitride semiconductor layer 5, preferably form dislocation in the stage that surpasses critical thickness.In addition,, for example 5nm enough little at the thickness of p type nitride-based semiconductor tunnel junction layer 6 or more hour also forms depletion layer in the 2nd p type nitride semiconductor layer 5, preferably can use be doped with p type impurity pass through composition formula In xGa 1-xThe nitride semiconductor crystal layer of N (0≤x＜1) expression.In above composition formula, x1 represents the In content ratio, and 1-x1 represents the Ga content ratio.Preferably, the doping density of the p type impurity of the 2nd p type nitride semiconductor layer 5 is 1 * 10 19/ cm 3Or it is higher.In the doping density of the p type impurity of the 2nd p type nitride semiconductor layer 5 less than 1 * 10 19/ cm 3Situation under, the resistance of the 2nd p type nitride semiconductor layer 5 increases, and may cause the driving voltage that increases.
For example, have for growth on it at a p type nitride semiconductor layer 4 under the situation of p type AlGaN layer of p type GaN layer, the 2nd p type nitride semiconductor layer 5 be preferably be doped with p type impurity pass through composition formula In X1G A1-x1The nitride semiconductor crystal layer of N (0≤x1＜1) expression.The superiors at a p type nitride semiconductor layer 4 are under the situation of p type AlGaN layer, and the 2nd p type nitride semiconductor layer 5 can be a p type GaN layer.In addition, reduce in order to prevent light output efficiency, the band-gap energy of the 2nd p type nitride semiconductor layer 5 can be equal to or greater than the energy of the optical wavelength of sending corresponding to luminescent layer 3.
In addition, as mentioned above, preferred p type nitride-based semiconductor tunnel junction layer 6 is the nitride-based semiconductor that contains In, and the ionized impurities density of preferred p type nitride-based semiconductor tunnel junction layer 6 is 1 * 10 18/ cm 3Or it is higher.
Relation for the band gap between a p type nitride semiconductor layer 4, the 2nd p type nitride semiconductor layer 5 and the p type nitride-based semiconductor tunnel junction layer 6, preferably the band gap of a p type nitride semiconductor layer 4 is greater than the band gap of the 2nd p type nitride semiconductor layer 5, and the band gap of the 2nd p type nitride semiconductor layer 5 is greater than the band gap of p type nitride-based semiconductor tunnel junction layer 6.Under the situation of band gap greater than the band gap of a p type nitride semiconductor layer 4 of the 2nd p type nitride semiconductor layer 5, thereby having the activation energy of increase, p type dopant causes the carrier density that reduces, may cause the driving voltage that increases.
In addition, as mentioned above, in order to increase tunnelling probability Tt, preferably n type nitride-based semiconductor tunnel junction layer 7 is the nitride-based semiconductor that contains In, and the ionized impurities density of preferred n type nitride-based semiconductor tunnel junction layer 7 is 1 * 10 18/ cm 3Or it is higher.Herein, because the ionized impurities density of n type nitride-based semiconductor tunnel junction layer 7 can be higher than the ionized impurities density of p type nitride semiconductor layer, so n type nitride-based semiconductor tunnel junction layer 7 can be for for example not containing the nitride-based semiconductor of In, such as GaN.
Because n type nitride-based semiconductor tunnel junction layer 7 has low donor level and high activating rate, so ionized impurities density can be higher, for example 1 * 10 19/ cm 3Or it is higher.In view of the tunnel junction depletion layer towards the little expansion of n type nitride-based semiconductor tunnel junction layer 7 and in view of the minimizing of the light amount of sending from luminescent layer 3 of being absorbed, the thickness of preferred n type nitride-based semiconductor tunnel junction layer 7 is 10nm or littler.
N type nitride-based semiconductor tunnel junction layer 7 can be doped with p type impurity with n type impurity.In this case, for example can be contemplated that be limited and formed intermediate level in depletion layer inside from the diffusion of the p type impurity of p type nitride-based semiconductor tunnel junction layer 6, this for example can help the improvement of tunnelling probability.
P type nitride-based semiconductor tunnel junction layer 6 and n type nitride-based semiconductor tunnel junction layer 7 can contain the layer and/or the unadulterated layer of films of opposite conductivity respectively.The layer of films of opposite conductivity and the respective thickness of undoped layer can be the thickness (for example 2nm or littler) that allows charge carrier tunnelling in tunnel junction.
In addition, reduce layer 8,, can suppress In from these layers evaporation so contain under the situation of In at p type nitride-based semiconductor tunnel junction layer 6 and/or n type nitride-based semiconductor tunnel junction layer 7 owing to formed the evaporation of n type nitride-based semiconductor.
, reduce layer 8 herein as n type nitride-based semiconductor evaporation, can use be doped with n type impurity pass through composition formula Al C1In D1Ga 1-(c1+d1)The nitride semiconductor crystal layer of N (0≤c1≤1,0≤d1≤1,0≤1-(c1+d1)≤1) expression especially preferably uses n type GaN.In above composition formula, c1 represents the Al content ratio, and d1 represents the In content ratio, 1-(c1+d1) expression Ga content ratio.
By forming the 2nd n type nitride semiconductor layer 9, can make the electric current diffusion of injecting from the p lateral electrode 11 that is formed on the 2nd n type nitride semiconductor layer 9.
,, preferably can use the nitride semiconductor crystal that is doped with n type impurity herein, especially preferred conductive formation as the 2nd n type nitride semiconductor layer 9.Particularly, required is that it is by having 1 * 10 18/ cm 3Or the GaN of higher carrier density forms.
In addition, as the n lateral electrode 10 and the p lateral electrode 11 that is formed on the 2nd n type nitride semiconductor layer 9 that are formed on the n type nitride semiconductor layer 2, for example, preferably can use at least a metal of from the group of Ti (titanium), Hf (hafnium) and Al (aluminium) formation, choosing to form electrode so that form ohmic contact.
Herein, can after the 2nd n type nitride semiconductor layer 9 of growing as mentioned above, second nitride semiconductor layer, 9 one sides from wafer expose the part of a n type nitride semiconductor layer 2 and form electrode, form n lateral electrode 10 on the surface that exposes by etching.
Alternatively, for the conductive support substrate of independent preparation, that side of the 2nd n type nitride semiconductor layer 9 of wafer after growth the 2nd n type nitride semiconductor layer 9 can be adhered to.Like this, a n type nitride semiconductor layer 2 one sides are light output sides, and the 2nd n type nitride semiconductor layer 9 one sides are support substrates sides.Can on the support substrates side, form at least a metal of from the group of Al, Pt and Ag formation, choosing of high reflectance.Thus, can make nitride semiconductor LED device with top and bottom electrode structure.
For the such nitride semiconductor LED device with top and bottom electrode structure, the 2nd n type nitride semiconductor layer 9 can have the higher carrier density of p type nitride semiconductor layer than routine.Therefore, irrelevant with the work function of metal, be easier to realize the ohm property that obtains by the charge carrier tunnelling.Therefore, can on the 2nd n type nitride semiconductor layer 9, form aforesaid high-reflectivity metal, show the trend that light output efficiency improves.
Second embodiment
Fig. 2 shows the schematic cross sectional view as the preferred embodiment of the nitride semiconductor LED device of an example of nitride semiconductor photogenerator of the present invention.Herein, nitride semiconductor LED device configuration shown in Figure 2 is for comprising substrate 21, and be deposited on a n type nitride semiconductor layer 22 on the substrate 21, luminescent layer 23, p type nitride semiconductor layer 24, p type nitride-based semiconductor tunnel junction layer 25, n type nitride-based semiconductor tunnel junction layer 26, the evaporation of n type nitride-based semiconductor in succession and reduce layer the 27 and the 2nd a n type nitride semiconductor layer 28, and have the n lateral electrode 29 that is formed on the n type nitride semiconductor layer 22 and be formed on p lateral electrode 30 on the 2nd n type nitride semiconductor layer 28.
The conventional structure that is formed on conventional p type nitride semiconductor layer place with positive electrode is compared, so the nitride semiconductor photogenerator of structure can have littler contact resistance, also can have the driving voltage that reduces, and the problem that will pay close attention to is how to reduce the loss of voltage at the tunnel junction place, and described tunnel junction is the knot between p type nitride-based semiconductor tunnel junction layer 25 and the n type nitride-based semiconductor tunnel junction layer 26.
Usually the tunnelling probability Tt that represents this tunnel junction by above expression formula (1).
In order to reduce the driving voltage of nitride semiconductor photogenerator, required is to increase this tunnelling probability Tt.From above expression formula (1) as can be seen, the possible method of increase tunnelling probability Tt is to reduce the energy gap Eg at tunnel junction place and increase the electric field ε that is applied to tunnel junction.
For for example disclosed conventional nitride semiconductor LED device that is constructed with the tunnel junction between p type InGaN layer and the n type InGaN layer in patent document 1, as the method for the energy gap Eg that reduces tunnel junction, can expect increasing the In content of p type InGaN layer and the In content of n type InGaN layer.Be applied to the method for the electric field ε of tunnel junction as increase, can expect increasing the ionized impurities density of p type InGaN and the ionized impurities density of n type InGaN layer.
Yet, for disclosed conventional nitride semiconductor LED device in the patent document 1, must be at growing p-type InGaN layer and growing n-type InGaN layer under 900 ℃ or the lower low temperature, to allow In involved with solid phase, this has caused the deterioration of these layers degree of crystallinity.In addition and since p type InGaN layer and n type InGaN layer each all be triple mixed crystals, so there are very many lattice defects such as point defect and line defect.In addition, in order to increase ionized impurities density, carry out the high density doping impurity.Because these factors, nitride semiconductor light-emitting diode device has the reliability of deterioration.
Therefore, inventor of the present invention studies comprehensively and has found to contain Al by the p type nitride-based semiconductor tunnel junction layer 25 that makes the formation tunnel junction and at least one in the n type nitride-based semiconductor tunnel junction layer 26, even under the situation that p type nitride-based semiconductor tunnel junction layer 25 and n type nitride-based semiconductor tunnel junction layer 26 are grown at low temperatures or carrying out under the situation of high density doping impurity for increasing ionized impurities concentration, also can improve reliability, and realized the present invention thus
, contain under the situation of Al at p type nitride-based semiconductor tunnel junction layer 25 and/or n type nitride-based semiconductor tunnel junction layer 26, aspect the increase of inhibition driving voltage, preferably Al content is 1 atomic percent or higher and 5 atomic percents or lower herein.For example, preferably will be by to composition formula Al X2In Y2Ga 1-(x2+y2)N (0.01＜x2≤0.05,0＜y2＜1, the material of the nitride semiconductor crystal doped p type impurity of the quaternary mixed crystal of the expression of x2＜y2) and/or the preparation of n type impurity is as p type nitride-based semiconductor tunnel junction layer 25 and/or n type nitride-based semiconductor tunnel junction layer 26.In above composition formula, x2 represents the Al content ratio, and y2 represents the In content ratio, 1-(x2+y2) expression Ga content ratio.
In order to reduce driving voltage, preferably the ionized impurities density of p type nitride-based semiconductor tunnel junction layer 25 is 1 * 10 18/ cm 3Or it is higher.Therefore, preferably the doping density of the p type impurity of p type nitride-based semiconductor tunnel junction layer 25 is 1 * 10 19/ cm 3Or it is higher.For the present invention, as p type impurity, for example can use Mg (magnesium) and/or Zn (zinc) to be used for mixing.
In addition, in order to reduce driving voltage, preferably the ionized impurities density of n type nitride-based semiconductor tunnel junction layer 26 is 1 * 10 19/ cm 3Or it is higher.Therefore, preferably the doping density of the n type impurity of n type nitride-based semiconductor tunnel junction layer 26 is 1 * 10 19/ cm 3Or it is higher.For the present invention, as n type impurity, for example can use Si (silicon) and/or Ge (germanium) to be used for mixing.
Because n type nitride-based semiconductor tunnel junction layer 26 has low donor level and high activating rate, so ionized impurities density can be higher, for example 1 * 10 19/ cm 3Or it is higher.In view of the tunnel junction depletion layer towards the little expansion of n type nitride-based semiconductor tunnel junction layer 26 and in view of the minimizing of the light amount of sending from luminescent layer 23 of being absorbed, the thickness of preferred n type nitride-based semiconductor tunnel junction layer 26 is 10nm or littler.
N type nitride-based semiconductor tunnel junction layer 26 can be doped with p type impurity with n type impurity.In this case, for example can be contemplated that be limited and formed intermediate level in depletion layer inside from the diffusion of the p type impurity of p type nitride-based semiconductor tunnel junction layer 25, this can help the improvement of tunnelling probability.
P type nitride-based semiconductor tunnel junction layer 25 and n type nitride-based semiconductor tunnel junction layer 26 can contain the layer and/or the unadulterated layer of films of opposite conductivity respectively.The layer of films of opposite conductivity and the respective thickness of undoped layer can be the thickness (for example 2nm or littler) that allows charge carrier tunnelling in tunnel junction.
As substrate 21, for example can use silicon substrate, silicon carbide substrates or zinc oxide substrate.
As a n type nitride semiconductor layer 22, for example can use the nitride semiconductor crystal that is doped with n type impurity.
As luminescent layer 23, for example can grow has the nitride semiconductor crystal of single quantum well (SQW) structure or Multiple Quantum Well (MQW) structure.Particularly, preferably use the luminescent layer that contains multi-quantum pit structure, described multi-quantum pit structure comprises the nitride semiconductor crystal of being represented by following composition formula:
Al a2In b2Ga 1-(a2+b2)N(0≤a2≤1，0≤b2≤1，0≤1-(a2+b2)≤1)
In described composition formula, a2 represents the content ratio of Al, and b2 represents the content ratio of In, the content ratio of 1-(a2+b2) expression Ga.
As p type nitride semiconductor layer 24, for example can use the nitride semiconductor crystal that is doped with p type impurity.Particularly, can use on it growth that the nitride semiconductor layer of the p type coating that having of p type GaN layer contain Al is arranged.
Reduce layer 27 owing to formed the evaporation of n type nitride-based semiconductor,, can suppress In from these layers evaporation so contain under the situation of In at p type nitride-based semiconductor tunnel junction layer 25 and/or n type nitride-based semiconductor tunnel junction layer 26.
, reduce layer 27 herein as n type nitride-based semiconductor evaporation, can use be doped with n type impurity pass through composition formula Al C2In D2Ga 1-(c2+d2)The nitride semiconductor crystal layer of N (0≤c2≤1,0≤d2≤1,0≤1-(c2+d2)≤1) expression especially preferably uses n type GaN.In above composition formula, c2 represents the Al content ratio, and d2 represents the In content ratio, 1-(c2+d2) expression Ga content ratio.In addition, preferably approximating growing n-type nitride-based semiconductor evaporation minimizing layer 27 under the temperature that is used for P type nitride-based semiconductor tunnel junction layer 25 and/or n type nitride-based semiconductor tunnel junction layer 26 greatly.
By forming the 2nd n type nitride semiconductor layer 28, can make the electric current diffusion of injecting from the p lateral electrode 30 that is formed on the 2nd n type nitride semiconductor layer 28.
,, preferably can use the nitride semiconductor crystal that is doped with n type impurity herein, especially preferred conductive formation as the 2nd n type nitride semiconductor layer 28.Particularly, it is desirable to have 1 * 10 18/ cm 3Or the GaN of higher carrier density.
As the n lateral electrode 29 and the p lateral electrode 30 that is formed on the 2nd n type nitride semiconductor layer 28 that are formed on the n type nitride semiconductor layer 22, for example, preferably can use from Ti (titanium), Hf (hafnium) and Al (aluminium) thus at least a metal of choosing the group that constitutes forms ohmic contact.
Herein, can after the 2nd n type nitride semiconductor layer 28 of growing as mentioned above, second nitride semiconductor layer, 28 1 sides from wafer expose the part of a n type nitride semiconductor layer 22 and form electrode, form n lateral electrode 29 on the surface that exposes by etching.
For choosing ground,, that side of the 2nd n type nitride semiconductor layer 28 of wafer after growth the 2nd n type nitride semiconductor layer 28 can be adhered to for the conductive support substrate of independent preparation.Like this, a n type nitride semiconductor layer 22 1 sides are light output sides, and the 2nd n type nitride semiconductor layer 28 1 sides are support substrates sides.Can on the support substrates side, form at least a metal of from the group of Al, Pt and Ag formation, choosing of high reflectance.Thus, can make nitride semiconductor LED device with top and bottom electrode structure.
For the such nitride semiconductor LED device with top and bottom electrode structure, the 2nd n type nitride semiconductor layer 28 can have the higher carrier density of p type nitride semiconductor layer than routine.Therefore, irrelevant with the work function of metal, be easier to realize the ohm property that obtains by the charge carrier tunnelling.Therefore, can on the 2nd n type nitride semiconductor layer 28, form aforesaid high-reflectivity metal, show the trend that light output efficiency improves.
Example 1
In example 1, make the nitride semiconductor LED device of as shown in the schematic cross sectional view of Fig. 3, constructing.Herein, nitride semiconductor LED device configuration in the example 1 is to be included in the GaN resilient coating 102 that deposits in the following order on the Sapphire Substrate 101, n type GaN lower floor 103, n type GaN contact layer 104, luminescent layer 105, p type AlGaN coating 106, p type GaN contact layer 107, p type InGaN layer 108, p type tunnel junction layer 109, n type tunnel junction layer 110, n type GaN evaporation reduces layer 111 and n type GaN layer 112, and has the n of being formed on type GaN layer 112 lip-deep pad electrode (pad electrode) 113 and be formed on n type GaN contact layer 104 lip-deep pad electrode 114.
At first, Sapphire Substrate 101 is set in the reactor of MOCVD equipment.When being applied to hydrogen in the reactor, the temperature of Sapphire Substrate 101 increases to 1050 ℃ of surfaces (c plane) with cleaning Sapphire Substrate 101.
Then, the temperature of Sapphire Substrate 101 is dropped to 510 ℃, and hydrogen is applied in the reactor as source material gas as carrier gas and with ammonia and TMG (trimethyl gallium), thereby go up the thickness of growing GaN resilient coating 102 to about 20nm on the surface (c plane) of Sapphire Substrate 101 by MOCVD.
Then, the temperature of Sapphire Substrate 101 is elevated to 1050 ℃, and with hydrogen as carrier gas, ammonia and TMG are applied in the reactor as foreign gas as source material gas and with silane, thereby the n type GaN lower floor 103 (carrier densities: 1 * 10 by MOCVD grow doping Si on GaN resilient coating 102 18/ cm 3) to the thickness of 6 μ m.
Then, mix to provide 5 * 10 except carrying out Si 18/ cm 3Carrier density outside, with n type GaN lower floor 103 similar modes, by the thickness of MOCVD growing n-type GaN contact layer 104 to 0.5 μ m in n type GaN lower floor 103.
Then, the temperature of Sapphire Substrate 101 is dropped to 700 ℃, and with hydrogen as carrier gas, ammonia, TMG and TMI (trimethyl indium) are applied in the reactor as source material gas, thus by MOCVD 6 In that cycling deposition 2.5nm is thick to replace on n type GaN contact layer 104 0.25Ga 0.75The GaN layer of N layer and 18nm forms the luminescent layer 105 with multi-quantum pit structure thus on n type GaN contact layer 104.It is evident that in the technology that forms luminescent layer 105, TMI is not applied in the reactor when the growing GaN layer.
Then, the temperature of Sapphire Substrate 101 is elevated to 950 ℃, and with hydrogen as carrier gas, with ammonia, TMG and TMA (trimethyl aluminium) as source material gas and with CP2Mg (bis-cyclopentadiene magnesium, cyclopentadienyl magnesium) being applied in the reactor as foreign gas, is 1 * 10 thereby by MOCVD grow doping on luminescent layer 105 density is arranged 20/ cm 3The Al of magnesium 0.15Ga 0.85The thickness of the p type AlGaN coating 106 to about 30nm that N constitutes.
Then, the temperature of Sapphire Substrate 101 is remained on 950 ℃, and with hydrogen as carrier gas, ammonia and TMG are applied in the reactor as foreign gas as source material gas and with CP2Mg, be 1 * 10 thereby density is arranged by MOCVD grow doping on p type AlGaN coating 106 20/ cm 3The thickness of p type GaN contact layer 107 to the 0.1 μ m that constitute of the GaN of magnesium.
Then, the temperature of Sapphire Substrate 101 is reduced to 700 ℃, and with nitrogen as carrier gas, ammonia, TMG and TMI are applied in the reactor as foreign gas as source material gas and with CP2Mg, thereby by MOCVD growing p-type InGaN layer 108 to 0 predetermined thickness to the 50nm scope on p type GaN contact layer 107, described p type InGaN layer 108 is that to be doped with density be 1 * 10 20/ cm 3The In of magnesium 0.25Ga 0.75The 2nd p type nitride semiconductor layer that N constitutes.
Then, the temperature of Sapphire Substrate 101 is reduced to 670 ℃, and with nitrogen as carrier gas, ammonia, TMG and TMI are applied in the reactor as foreign gas as source material gas and with CP2Mg, be 1 * 10 thereby density is arranged by MOCVD grow doping on p type InGaN layer 108 20/ cm 3The In of magnesium 0.30Ga 0.70The thickness of the p type tunnel junction layer 109 to 2nm that N constitutes.
Afterwards, the temperature of Sapphire Substrate 101 is remained on 670 ℃, and with nitrogen as carrier gas, ammonia, TMG and TMI are applied in the reactor as foreign gas as source material gas and with silane, thereby the In of Si are arranged by MOCVD grow doping on p type tunnel junction layer 109 0.30Ga 0.70The n type tunnel junction layer 110 (carrier densities: 5 * 10 that N constitutes 19/ cm 3) to the thickness of 4nm.
Then, the temperature of Sapphire Substrate 101 is remained on 670 ℃, and with nitrogen as carrier gas, ammonia and TMG are applied in the reactor as foreign gas as source material gas and with silane, thereby the n type GaN evaporation that grow doping has the GaN of Si to constitute on n type tunnel junction layer 110 reduces layer 111 (carrier density: 5 * 10 19/ cm 3) to the thickness of 15nm.
Afterwards, the temperature of Sapphire Substrate 101 is elevated to 950 ℃, and with hydrogen as carrier gas, ammonia and TMG are applied in the reactor as foreign gas as source material gas and with silane, density is arranged is 1 * 10 thereby reduce on the layer 111 grow doping by MOCVD in n type GaN evaporation 19/ cm 3The thickness of n type GaN layer 112 to the 0.2 μ m that constitute of the GaN of Si.
Then, the temperature of Sapphire Substrate 101 is reduced to 700 ℃, and nitrogen is applied in the reactor to anneal as carrier gas.
Wafer after reactor is removed annealing, in the wafer the superiors, be on the surface of n type GaN layer 112, the mask of formation patterning.By RIE (reactive ion etching), thus the part surface of carving the part exposure n type GaN contact layer 104 of wafer from 112 1 lateral erosion of n type GaN layer.
Then, on the surface of n type GaN layer 112, form pad electrode 113, and on n type GaN contact layer 104, form pad electrode 114.Herein, by depositing Ti layer and Al layer form pad electrode 113 and pad electrode 114 simultaneously in succession on the respective surfaces of n type GaN layer 112 and n type GaN contact layer 104.Afterwards, thus wafer is divided into nitride semiconductor LED device in the example 1 that the manufacturing of a plurality of chips has structure shown in the schematic cross sectional view among Fig. 3.
Fig. 4 shows the relation between the thickness of nitride semiconductor LED device drive voltage and p type InGaN layer 108 in the example 1.In Fig. 4, the longitudinal axis is represented the driving voltage (V) when injecting the electric current of 20mA, and transverse axis is represented the thickness (nm) of p type InGaN layer 108.
As shown in Figure 4, driving voltage reduces along with the increase of p type InGaN layer 108 thickness, until the thickness of the 20nm that arrives p type InGaN layer 108.At the thickness as the p type InGaN layer 108 of the 2nd p type nitride semiconductor layer is 10nm or more hour, confirmable is that driving voltage significantly reduces.
Example 2
Under the condition identical and by the method identical, make the nitride semiconductor LED device, until the step of growing p-type GaN contact layer 107 with example 1 with example 1.
The temperature of Sapphire Substrate 101 is reduced to 700 ℃, and with nitrogen as carrier gas, ammonia, TMG and TMI are applied in the reactor as foreign gas as source material gas and with CP2Mg, thereby by the thickness of MOCVD growing p-type InGaN layer 108 to 20nm on p type GaN contact layer 107, described p type InGaN layer 108 is that to be doped with density be 1 * 10 20/ cm 3The In of magnesium 0.25Ga 0.75The 2nd p type nitride semiconductor layer that N constitutes.
Then, the temperature of Sapphire Substrate 101 is reduced to 670 ℃, and with nitrogen as carrier gas, ammonia, TMG and TMI are applied in the reactor as foreign gas as source material gas and with CP2Mg, be 1 * 10 thereby density is arranged by MOCVD grow doping on p type InGaN layer 108 20/ cm 3The In of magnesium 0.30Ga 0.70The predetermined thickness of the p type tunnel junction layer 109 to 0 that N constitutes to the 10nm scope.
Afterwards, under the condition identical and by the method identical, make the nitride semiconductor LED device in the example 2 with example 1 with example 1.
Fig. 5 shows the relation between the thickness of nitride semiconductor LED device drive voltage and p type tunnel junction layer 109 in the example 2.In Fig. 5, the longitudinal axis is represented the driving voltage (V) when injecting the electric current of 20mA, and transverse axis is represented the thickness (nm) of p type tunnel layer 109.
As shown in Figure 5, be that driving voltage reduces under 5nm or the littler situation at the thickness of p type tunnel junction layer 109.At the thickness of p type tunnel junction layer 109 is that driving voltage particularly reduces under 1nm or bigger and 3nm or the littler situation.
Fig. 6 shows the relation between the thickness of the light output of nitride semiconductor LED device in the example 2 and p type tunnel junction layer 109.In Fig. 6, the longitudinal axis is represented light output (.a.u) and transverse axis is represented the thickness (nm) of p type tunnel junction layer 109.
As shown in Figure 6, confirmable is that light output increases along with p type tunnel junction layer 109 reducing of thickness.
From the result of Fig. 5 and 6, confirmablely be, reduce driving voltage and improving the light output facet, preferably the thickness of p type tunnel junction layer 109 is 5nm or littler, more preferably is 1nm or bigger and 3nm or littler.
Example 3
In example 3, make the nitride semiconductor LED device of shown in the schematic cross sectional view of Fig. 7, constructing.Herein, the nitride semiconductor LED device configuration in the example 3 is to be included in ohmic contact layer 56, the first jointing metal layer (firstbonding metal layer), 57, the second jointing metal layer 54, barrier layer 53, reflector 52, n type GaN layer 112, n type GaN evaporation reducing layer 111, n type tunnel junction layer 110, p type tunnel junction layer 109, p type InGaN layer 108, p type GaN contact layer 107, p type AlGaN coating 106, luminescent layer 105, n type GaN contact layer 104, n type GaN lower floor 103 and the pad electrode 58 that deposits in succession on the conductive substrates 55.
In example 3, to make the step of diode component until growing p-type GaN contact layer 107 with example 1 similar mode.
Then, the temperature of Sapphire Substrate 101 is reduced to 700 ℃, and with nitrogen as carrier gas, ammonia, TMG and TMI are applied in the reactor as foreign gas as source material gas and with CP2Mg, thereby by the thickness of MOCVD growing p-type InGaN layer 108 to 20nm on p type GaN contact layer 107, described p type InGaN layer 108 is that to be doped with density be 1 * 10 20/ cm 3The In of magnesium 0.25Ga 0.75The 2nd p type nitride semiconductor layer that N constitutes.
Then, the temperature of Sapphire Substrate 101 is reduced to 670 ℃, and with nitrogen as carrier gas, ammonia, TMG and TMI are applied in the reactor as foreign gas as source material gas and with CP2Mg, be 1 * 10 thereby density is arranged by MOCVD grow doping on p type InGaN layer 108 20/ cm 3The In of magnesium 0.30Ga 0.70The thickness of the p type tunnel junction layer 109 to 2nm that N constitutes.
Afterwards, the temperature of Sapphire Substrate 101 is remained on 670 ℃, and with nitrogen as carrier gas, ammonia, TMG and TMI are applied in the reactor as foreign gas as source material gas and with silane, thereby the In of Si are arranged by MOCVD grow doping on p type tunnel junction layer 109 0.30Ga 0.70The n type tunnel junction layer 110 (carrier densities: 5 * 10 that N constitutes 19/ cm 3) to the thickness of 4nm.
Then, the temperature of Sapphire Substrate 101 is remained on 670 ℃, and with nitrogen as carrier gas, ammonia and TMG are applied in the reactor as foreign gas as source material gas and with silane, thereby the n type GaN evaporation that grow doping has the GaN of Si to constitute on n type tunnel junction layer 110 reduces layer 111 (carrier density: 5 * 10 19/ cm 3) to the thickness of 15nm.
Afterwards, the temperature of Sapphire Substrate 101 is elevated to 950 ℃, and with hydrogen as carrier gas, ammonia and TMG are applied in the reactor as foreign gas as source material gas and with silane, density is arranged is 1 * 10 thereby reduce on the layer 111 grow doping by MOCVD in n type GaN evaporation 19/ cm 3The thickness of n type GaN layer 112 to the 0.2 μ m that constitute of the GaN of Si.
Then, the temperature of Sapphire Substrate 101 is reduced to 700 ℃, and nitrogen is applied in the reactor to anneal as carrier gas.
After annealing, on the surface of n type GaN layer 112, the second jointing metal layer 54 that the Au layer that barrier layer 53 that forms by the Mo layer that EB (electron beam) vapour deposition formation in the following order thickness is the reflector 52 that forms of the Ag layer of 150nm, thickness is 50nm and thickness are 3 μ m forms.
Then, thickness in preparation separately is on the conductive substrates 55 that is formed by conduction Si of 120 μ m, the thickness that uses the EB vapour deposition to deposit in the following order to contain deposition in the following order is the Ti layer of 15nm and the thickness ohmic electrode layer 56 as the Al layer of 150nm, and contains in the following order that the thickness of deposition is the Au layer of 100nm and the first jointing metal layer 57 of the AuSn layer that thickness is 3 μ m.
Then, the Au layer that is positioned at the AuSn layer of the superficial layer of the first jointing metal layer 57 and is positioned at the superficial layer of the second jointing metal layer 54 is set to toward each other.Use the eutectic bond method to come in conjunction with the first jointing metal layer 57 and the second jointing metal layer 54.Temperature in the eutectic bond technology is arranged on 290 ℃.
Then, utilize the triple-frequency harmonics (wavelength: 355nm) come radiation of YAG laser emission by the rear surface side of bright finished Sapphire Substrate 101, thereby make the GaN resilient coating 102 that is formed on the Sapphire Substrate 101 and the interface portion thermal decomposition between the n type GaN lower floor 103, thereby remove Sapphire Substrate 101 and GaN resilient coating 102.
Afterwards, on because of the surface of removing the n type GaN lower floor 103 that Sapphire Substrate 101 and GaN resilient coating 102 expose, sequential aggradation Ti layer and Au layer, thereby formation pad electrode 58.Be divided into a plurality of chips to make the nitride semiconductor LED device in the example 3 of as shown in the schematic cross sectional view of Fig. 7, constructing with forming pad electrode 58 wafer afterwards.For the nitride semiconductor LED device in the example 3, in order to reduce the contact resistance between n type GaN lower floor 103 and the pad electrode 58, the carrier density of n type GaN lower floor 103 is set to 5 * 10 18/ cm 3
Identifiablely be, for the nitride semiconductor LED device in the example 3, driving voltage is 4.0V when injecting the electric current of 20mA, and this is lower than the top with the following stated and the conventional semiconductor light emitting diode device (the nitride semiconductor LED device in the comparative example 1) of bottom electrode structure.
Comparative example 1
In comparative example 1, make the nitride semiconductor LED device of shown in the schematic cross sectional view of Fig. 8, constructing.Herein, the nitride semiconductor LED device configuration in the comparative example 1 is to be included in ohmic contact layer 56, the first bond layer 57, the second bond layer 54, barrier layer 53, reflector 52, p type GaN contact layer 107, p type AlGaN coating 106, luminescent layer 105, n type GaN contact layer 104, n type GaN lower floor 103 and the pad electrode 58 that deposits in succession on the conductive substrates 55.
Except n type GaN layer 112, n type GaN evaporation reducing layer 111, n type tunnel junction layer 110, p type tunnel junction layer 109, p type InGaN layer 108, the nitride semiconductor LED device in the comparative example 1 is constructed to identical with nitride semiconductor LED device in the example 3.
For the nitride semiconductor LED device in the comparative example 1, driving voltage is 6.0V when injecting the electric current of 20mA.Identifiable is that this driving voltage is higher than the nitride semiconductor LED device drive voltage of example 3 when injecting the electric current of 20mA.A reason is that the reflector 52 and the contact resistance between the p type GaN contact layer 107 that are formed by the Ag layer are higher.
For the nitride semiconductor LED device in the comparative example 1, in order to reduce driving voltage, can use the film that between p type GaN contact layer 107 and the reflector 52 that forms by the Ag layer, forms several approximately nm such as the metal of Pd or Ni with high work function.Yet, in this case, because the antiradar reflectivity of Pd and Ni, reduced light output thereby may be absorbed from the light of luminescent layer 105.
Example 4
In example 4, make the nitride semiconductor LED device of as shown in the schematic cross sectional view of Fig. 9, constructing.Herein, nitride semiconductor LED device configuration in the example 4 is to be included in the GaN resilient coating 202, n type GaN lower floor 203, n type GaN contact layer 204, luminescent layer 205, p type AlGaN coating 206, p type GaN contact layer 207, p type tunnel junction layer 208, n type tunnel junction layer 209, the n type GaN evaporation that deposit in the following order on the Sapphire Substrate 201 to reduce layer 210 and n type GaN layer 211, and has the n of being formed on type GaN layer 211 lip-deep pad electrode 212 and be formed on n type GaN contact layer 204 lip-deep pad electrode 213.
At first, Sapphire Substrate 201 is set in the reactor of MOCVD equipment.When being applied to hydrogen in the reactor, the temperature of Sapphire Substrate 201 increases to 1050 ℃ of surfaces (c plane) with cleaning Sapphire Substrate 201.
Then, the temperature of Sapphire Substrate 201 is dropped to 510 ℃, and hydrogen is applied in the reactor as source material gas as carrier gas and with ammonia and TMG (trimethyl gallium), thereby go up the thickness that forms GaN resilient coating 202 to about 20nm on the surface (c plane) of Sapphire Substrate 201 by MOCVD.
Then, the temperature of Sapphire Substrate 201 is elevated to 1050 ℃, and with hydrogen as carrier gas, ammonia and TMG are applied in the reactor as foreign gas as source material gas and with silane, thereby the n type GaN lower floor 203 (carrier densities: 1 * 10 by MOCVD grow doping Si on GaN resilient coating 202 18/ cm 3) to the thickness of 6 μ m.
Then, mix to provide 5 * 10 except carrying out Si 18/ cm 3Carrier density outside, with n type GaN lower floor 203 similar modes, by the thickness of MOCVD growing n-type GaN contact layer 204 to 0.5 μ m in n type GaN lower floor 203.
Then, the temperature of Sapphire Substrate 201 is dropped to 700 ℃, and with hydrogen as carrier gas, ammonia, TMG and TMI (trimethyl indium) are applied in the reactor as source material gas, thus by MOCVD 6 In that cycling deposition 2.5nm is thick to replace on n type GaN contact layer 204 0.25Ga 0.75The GaN layer that N layer and 18nm are thick forms the luminescent layer 205 with multi-quantum pit structure thus on n type GaN contact layer 204.It is evident that in the technology that forms luminescent layer 205, TMI is not applied in the reactor when the growing GaN layer.
Then, the temperature of Sapphire Substrate 201 is elevated to 950 ℃, and with hydrogen as carrier gas, with ammonia, TMG and TMA (trimethyl aluminium) as source material gas and with CP2Mg (bis-cyclopentadiene magnesium, cyclopentadienyl magnesium) being applied in the reactor as foreign gas, is 1 * 10 thereby by MOCVD grow doping on luminescent layer 205 density is arranged 20/ cm 3The Al of magnesium 0.15Ga 0.85The thickness of the p type AlGaN coating 206 to about 30nm that N constitutes.
Then, the temperature of Sapphire Substrate 201 is remained on 950 ℃, and with hydrogen as carrier gas, ammonia and TMG are applied in the reactor as foreign gas as source material gas and with CP2Mg, be 1 * 10 thereby density is arranged by MOCVD grow doping on p type AlGaN coating 206 20/ cm 3The thickness of p type GaN contact layer 207 to the 0.1 μ m that constitute of the GaN of magnesium.
Then, the temperature of Sapphire Substrate 201 is reduced to 700 ℃, and with nitrogen as carrier gas, ammonia, TMA, TMG and TMI are applied in the reactor as foreign gas as source material gas and with CP2Mg, be 1 * 10 thereby density is arranged by MOCVD grow doping on p type GaN contact layer 207 20/ cm 3The Al of Mg xIn yGa 1-(x+y)N (0≤x≤0.05, y=0.25) thickness of the p type tunnel junction layer 208 to 20nm of Gou Chenging.
Afterwards, the temperature of Sapphire Substrate 201 is remained on 700 ℃, and with nitrogen as carrier gas, ammonia, TMA, TMG and TMI are applied in the reactor as foreign gas as source material gas and with silane, thereby the Al of Si are arranged by MOCVD grow doping on p type tunnel junction layer 208 xIn yGa 1-(x+y)N (0≤x≤0.05, y=0.25) constitute n type tunnel junction layer 209 (carrier densities: 5 * 10 19/ cm 3) to the thickness of 4nm.In n type tunnel junction layer 209, the content of Al is identical with the content of Al in the p type tunnel junction layer 208.
It is evident that, do not contain at p type tunnel junction layer 208 and n type tunnel junction layer 209 under the situation of Al (being x=0), do not apply TMA.
Then, the temperature of Sapphire Substrate 201 is remained on 700 ℃, and with nitrogen as carrier gas, ammonia and TMG are applied in the reactor as foreign gas as source material gas and with silane, thereby the n type GaN evaporation that grow doping has the GaN of Si to constitute on n type tunnel junction layer 209 reduces layer 210 (carrier density: 5 * 10 19/ cm 3) to the thickness of 15nm.
Afterwards, the temperature of Sapphire Substrate 201 is elevated to 950 ℃, and with hydrogen as carrier gas, ammonia and TMG are applied in the reactor as foreign gas as source material gas and with silane, density is arranged is 1 * 10 thereby reduce on the layer 210 grow doping in n type GaN evaporation 19/ cm 3The thickness of n type GaN layer 211 to the 0.2 μ m that constitute of the GaN of Si.
Then, the temperature of Sapphire Substrate 201 is reduced to 700 ℃, and nitrogen is applied in the reactor to anneal as carrier gas.
Wafer after reactor is removed annealing, in the wafer the superiors, be on the surface of n type GaN layer 211, formation is with the mask of reservation shape composition.By RIE (reactive ion etching), thus the part surface of carving the part exposure n type GaN contact layer 204 of wafer from 211 1 lateral erosion of n type GaN layer.
Then, on the surface of n type GaN layer 211, form pad electrode 212, and on n type GaN contact layer 204, form pad electrode 213.Herein, by depositing Ti layer and Al layer form pad electrode 212 and pad electrode 213 simultaneously in succession on the respective surfaces of n type GaN layer 211 and n type GaN contact layer 204.Afterwards, thus wafer is divided into nitride semiconductor LED device in the example 4 that the manufacturing of a plurality of chips has structure shown in the schematic cross sectional view among Fig. 9.
Figure 10 shows the relation between the Al content of the breakdown current density of nitride semiconductor LED device in the example 4 and p type tunnel junction layer 208 and n type tunnel junction layer 209.Thereby breakdown current density refers to when tunnel junction is breakdown and stops the density of injection current when luminous.In Figure 10, the longitudinal axis is represented breakdown current density (A/cm 2), transverse axis is represented the Al content (atomic percent) of p type tunnel junction layer 208 and n type tunnel junction layer 209.
As shown in figure 10, be not less than 1 atomic percent and be not more than under the situation in the scope of 5 atomic percents at the Al content of p type tunnel junction layer 208 and n type tunnel junction layer 209, surpass the situation be not less than 1 atomic percent and be not more than the scope of 5 atomic percents with Al content and compare, breakdown current density enlarges markedly.
Figure 11 shows the relation between the Al content of nitride semiconductor LED device drive voltage and p type tunnel junction layer 208 and n type tunnel junction layer 209 in the example 4.In Figure 11, the longitudinal axis is represented the driving voltage (V) when injecting the electric current of 20mA, and transverse axis is represented the Al content (atomic percent) of p type tunnel junction layer 208 and n type tunnel junction layer 209.
As shown in figure 11, surpass the point of 5 percentages from the Al content of p type tunnel junction layer 208 and n type tunnel junction layer 209, driving voltage sharply increases.Therefore, preferably, the Al content of p type tunnel junction layer 208 and n type tunnel junction layer 209 is 5 atomic percents or littler.
Therefore, find out that preferably the Al content of p type tunnel junction layer 208 and n type tunnel junction layer 209 is 1 atomic percent or bigger and 5 atomic percents or littler from above result.
Example 5
Under the condition identical and by the method identical, make the nitride semiconductor LED device, until the step of growing p-type GaN contact layer 207 with example 4 with example 4.
After growing p-type GaN contact layer 207, the temperature of Sapphire Substrate 201 is reduced to 700 ℃, and with nitrogen as carrier gas, ammonia, TMA, TMG and TMI are applied in the reactor as foreign gas as source material gas and with CP2Mg, are 1 * 10 thereby by MOCVD grow doping on p type GaN contact layer 207 density is arranged 20/ cm 3The Al of magnesium 0.02In 0.25Ga 0.73The thickness of the p type tunnel junction layer 208 to 20nm that N constitutes.
Afterwards, the temperature of Sapphire Substrate 201 is remained on 700 ℃, and with nitrogen as carrier gas, ammonia, TMG and TMI are applied in the reactor as foreign gas as source material gas and with silane, thereby the In of Si are arranged by MOCVD grow doping on p type tunnel junction layer 208 0.25Ga 0.75The n type InGaN tunnel junction layer 209 (carrier densities: 5 * 10 that N constitutes 19/ cm 3) to the thickness of 4nm.
Afterwards, under the condition identical and by the method identical, make the nitride semiconductor LED device in the example 5 with example 4 with example 4.
The breakdown current density of the nitride semiconductor LED device in the assessment example 5.Find that this breakdown current density is higher than the breakdown current density of the nitride semiconductor LED device in the comparative example 2 of the following stated, makes reliability higher thus.
Example 6
Under the condition identical and by the method identical, make the nitride semiconductor LED device, until the step of growing p-type GaN contact layer 207 with example 4 with example 4.
After growing p-type GaN contact layer 207, the temperature of Sapphire Substrate 201 is reduced to 700 ℃, and with nitrogen as carrier gas, ammonia, TMG and TMI are applied in the reactor as foreign gas as source material gas and with CP2Mg, are 1 * 10 thereby by MOCVD grow doping on p type GaN contact layer 207 density is arranged 20/ cm 3The In of magnesium 0.25Ga 0.75The thickness of the p type tunnel junction layer 208 to 20nm that N constitutes.
Afterwards, the temperature of Sapphire Substrate 201 is remained on 700 ℃, and with nitrogen as carrier gas, ammonia, TMA, TMG and TMI are applied in the reactor as foreign gas as source material gas and with silane, thereby the Al of Si are arranged by MOCVD grow doping on p type tunnel junction layer 208 0.02In 0.25Ga 0.73The n type InGaN tunnel junction layer 209 (carrier densities: 5 * 10 that N constitutes 19/ cm 3) to the thickness of 4nm.
Afterwards, under the condition identical and by the method identical, make the nitride semiconductor LED device in the example 6 with example 4 with example 4.
The breakdown current density of the nitride semiconductor LED device in the assessment example 6.This breakdown current density is higher than the breakdown current density of the nitride semiconductor LED device in the comparative example 2 of the following stated, makes reliability higher thus.
Comparative example 2
Under the condition identical and by the method identical, make the nitride semiconductor LED device, until the step of growing p-type GaN contact layer 207 with example 4 with example 4.
After growing p-type GaN contact layer 207, the temperature of Sapphire Substrate 201 is reduced to 700 ℃, and with nitrogen as carrier gas, ammonia, TMG and TMI are applied in the reactor as foreign gas as source material gas and with CP2Mg, are 1 * 10 thereby by MOCVD grow doping on p type GaN contact layer 207 density is arranged 20/ cm 3The In of magnesium 0.25Ga 0.75The thickness of the p type tunnel junction layer 208 to 20nm that N constitutes.
Afterwards, the temperature of Sapphire Substrate 201 is remained on 700 ℃, and with nitrogen as carrier gas, ammonia, TMG and TMI are applied in the reactor as foreign gas as source material gas and with silane, thereby the In of Si are arranged by MOCVD grow doping on p type tunnel junction layer 208 0.25Ga 0.75The n type InGaN tunnel junction layer 209 (carrier densities: 5 * 10 that N constitutes 19/ cm 3) to the thickness of 4nm.
Afterwards, under the condition identical and by the method identical, make the nitride semiconductor LED device in the comparative example 2 with example 4 with example 4.
The breakdown current density of the nitride semiconductor LED device in the comparative example 2 is lower than the corresponding breakdown current density of the nitride semiconductor LED device in example 5 and 6, makes reliability lower thus.
According to the present invention, can reduce the driving voltage of nitride semiconductor photogenerator, this nitride semiconductor photogenerator is such as being the nitride semiconductor LED device that has tunnel junction and launch blue light (wavelength: for example 430nm or bigger and 490nm or littler).
According to the present invention, can improve the reliability of nitride semiconductor photogenerator, this nitride semiconductor photogenerator is such as being the nitride semiconductor LED device that has tunnel junction and launch blue light (wavelength: for example 430nm or bigger and 490nm or littler).
Although described and shown in detail the present invention, should know to be understood that, the mode by diagram and example but not represent the present invention only by the mode of restriction, scope of the present invention is explained by the clause of claims.
This non-provisional application is based on the Japanese patent application No.2006-315298 and the 2006-327124 that submit in Japan Patent office respectively on November 22nd, 2006 and on December 4th, 2006, and its full content is hereby incorporated by.

Claims (13)

1. nitride semiconductor photogenerator comprises:
Substrate;
Be formed on the n type nitride semiconductor layer on the described substrate;
Be formed on the luminescent layer on the described n type nitride semiconductor layer;
Be formed on the p type nitride semiconductor layer on the described luminescent layer;
Be formed on the p type nitride-based semiconductor tunnel junction layer on the described p type nitride semiconductor layer;
Be formed on the n type nitride-based semiconductor tunnel junction layer on the described p type nitride-based semiconductor tunnel junction layer; And
Be formed on the 2nd n type nitride semiconductor layer on the described n type nitride-based semiconductor tunnel junction layer; And
Wherein said p type nitride-based semiconductor tunnel junction layer and described n type nitride-based semiconductor tunnel junction layer form tunnel junction, and in described p type nitride-based semiconductor tunnel junction layer and the described n type nitride-based semiconductor tunnel junction layer at least one comprises aluminium;
The aluminium content of at least one in wherein said p type nitride-based semiconductor tunnel junction layer and the described n type nitride-based semiconductor tunnel junction layer is for being not less than 1 atomic percent and being not more than 5 atomic percents.
2. nitride semiconductor photogenerator according to claim 1, wherein said p type nitride-based semiconductor tunnel junction layer comprises aluminium and indium, and indium content is higher than aluminium content.
3. nitride semiconductor photogenerator according to claim 1, wherein said n type nitride-based semiconductor tunnel junction layer comprises aluminium and indium, and indium content is higher than aluminium content.
4. nitride semiconductor photogenerator according to claim 1, wherein said p type nitride-based semiconductor tunnel junction layer is doped with doping density and is not less than 1 * 10 19/ cm 3P type impurity.
5. nitride semiconductor photogenerator according to claim 1, wherein said n type nitride-based semiconductor tunnel junction layer is doped with doping density and is not less than 1 * 10 19/ cm 3N type impurity.
6. nitride semiconductor photogenerator according to claim 1, wherein said n type nitride-based semiconductor tunnel junction layer has the thickness that is not more than 10nm.
7. nitride semiconductor photogenerator comprises:
Substrate;
Be formed on the n type nitride semiconductor layer on the described substrate;
Be formed on the luminescent layer on the described n type nitride semiconductor layer, described luminescent layer emission has the blue light of 430nm to the wavelength of 490nm;
Be formed on the p type nitride semiconductor layer on the described luminescent layer;
Be formed on the p type nitride-based semiconductor tunnel junction layer on the described p type nitride semiconductor layer;
Be formed on the n type nitride-based semiconductor tunnel junction layer on the described p type nitride-based semiconductor tunnel junction layer; And
Be formed on the 2nd n type nitride semiconductor layer on the described n type nitride-based semiconductor tunnel junction layer; And
Wherein said p type nitride-based semiconductor tunnel junction layer and described n type nitride-based semiconductor tunnel junction layer form tunnel junction, and in described p type nitride-based semiconductor tunnel junction layer and the described n type nitride-based semiconductor tunnel junction layer at least one comprises aluminium.
8. nitride semiconductor photogenerator according to claim 7, the aluminium content of at least one in wherein said p type nitride-based semiconductor tunnel junction layer and the described n type nitride-based semiconductor tunnel junction layer is for being not less than 1 atomic percent and being not more than 5 atomic percents.
9. nitride semiconductor photogenerator according to claim 8, wherein said p type nitride-based semiconductor tunnel junction layer comprises aluminium and indium, and indium content is higher than aluminium content.
10. nitride semiconductor photogenerator according to claim 8, wherein said n type nitride-based semiconductor tunnel junction layer comprises aluminium and indium, and indium content is higher than aluminium content.
11. nitride semiconductor photogenerator according to claim 7, wherein said p type nitride-based semiconductor tunnel junction layer is doped with doping density and is not less than 1 * 10 19/ cm 3P type impurity.
12. nitride semiconductor photogenerator according to claim 7, wherein said n type nitride-based semiconductor tunnel junction layer is doped with doping density and is not less than 1 * 10 19/ cm 3N type impurity.
13. nitride semiconductor photogenerator according to claim 7, wherein said n type nitride-based semiconductor tunnel junction layer has the thickness that is not more than 10nm.
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US20100308300A1 (en) * 2009-06-08 2010-12-09 Siphoton, Inc. Integrated circuit light emission device, module and fabrication process
CN104682195A (en) * 2015-02-13 2015-06-03 北京牡丹视源电子有限责任公司 Edge emitting semiconductor laser with tunnel junction structure and preparation method thereof
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CN102237463B (en) * 2010-04-23 2016-01-27 Lg伊诺特有限公司 Luminescent device and manufacture method, light emitting device package and luminescent system

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