The n type contact layer structure of gallium nitride multiple quantum trap luminous diode
Technical field
The present invention is relevant gallium nitride multiple quantum trap luminous diode, the structure of the low-resistance n type contact layer in the particularly relevant gallium nitride multiple quantum trap luminous diode.
Background technology
Because gallium nitride (GaN) light-emitting diode can reach required energy gap (Band Gap) by the composition of control material, therefore can produce various coloured light, especially need the blue light or the purple-light LED of high energy gap.Therefore the correlation technique of gallium nitride light-emitting diode becomes the actively emphasis of research and development of industry.
A kind of luminescent layer of known gallium nitride light-emitting diode mainly is with gallium nitride and InGaN In
xGa
1-xN, (0≤x≤1) is that (Multi-quantum Well, MQW) structure utilize electronics and electric hole at In to a multiple quantum trap of well (Potential Well)
xGa
1-xN (0≤x≤1) position well in conjunction with and discharge photon.Under this luminescent layer, generally be to adopt the n type gallium nitride contact layer that n type doping (for example, silicon) is arranged.
For making this n type gallium nitride contact layer reach low-resistance requirement, generally be to adopt doped with high concentration (>1 * 10
19Cm
-3) silicon (Si) make n type gallium nitride contact layer.But find that in actual manufacture process n type gallium nitride contact layer tends to because of the heavily doped result of silicon, do not form excessive stress, cause easily giving birth to be full of cracks, even the phenomenon of fracture because lattice matches.These phenomenons not only influence the quality bills of materials of n type gallium nitride contact layer, also can be increased in the difficulty that next step is made n type Ohm contact electrode in the processing procedure above n type gallium nitride contact layer.These shortcomings make the gallium nitride multiple quantum trap luminous diode produce whole electric properties deteriorate or conduct electricity badly, even become waste product.Influence in one's power, these gallium nitride multiple quantum trap luminous diodes need higher operating voltage on the one hand, and the electrical power of consumption increases when making running, are the acceptance rate decline of making on the other hand, and production cost improves.
In addition, silicon heavy doping also forms point defect (Pin Hole) easily in the result of n type gallium nitride contact layer, makes the whole diode characteristic variation of gallium nitride multiple quantum trap luminous diode, and has the generation of leakage current in operation.
Summary of the invention
Therefore, in order to overcome the defective of above-mentioned prior art, the present invention proposes the structure of several n type gallium nitride contact layers, to solve foregoing problems.
The invention provides a kind of n type contact layer structure of gallium nitride multiple quantum trap luminous diode, this gallium nitride multiple quantum trap luminous diode comprises respectively from going up order down:
Substrate is by alumina single crystal, 6H-SiC, 4H-SiC, Si, ZnO, GaAs, spinelle (MgAl
2O
4) approach nitride-based semiconductor with lattice constant one of monocrystalline oxide made;
Be positioned at a side of this substrate and by aluminum indium gallium nitride Al with specific composition
1-a-bGa
aIn
bThe resilient coating that N constituted, 0≤a, b<1, a+b≤1;
Be positioned at this n type contact layer on this resilient coating;
Be positioned on this n type contact layer, cover this n type contact layer partly the surface, by luminescent layer that InGaN constituted;
In this luminescent layer the same side and be positioned at the negative electrode of this n type contact layer surface on not being capped partly;
Be positioned on this luminescent layer, by there being magnesium to mix, have the aluminum indium gallium nitride Al of a specific composition
1-c-dGa
cIn
dThe p type coating that N constituted, 0≤c, d<1, c+d≤1;
Be positioned on this p type coating, by there being magnesium to mix, have the aluminum indium gallium nitride Al of another specific composition
1-e-fGa
eIn
fThe p type contact layer that N constituted, 0≤e, f<1, e+f≤1; And
Be positioned on this p type contact layer, cover the partly positive electrode on p type contact layer surface,
Wherein, this n type contact layer is first basic unit that is constituted by first number of plies altogether, by n type III group-III nitride, with second number of plies altogether, by the formed superlattice structure of the mutual stack of second basic unit of n type III group-III nitride, the energy gap of this second basic unit is high than this first basic unit, its bottom is one of this first basic unit and this second basic unit, and its superiors are one of this first basic unit and this second basic unit.
The present invention forms different Al for two kinds by combination
mIn
nGa
1-m-nN and Al
pIn
qGa
1-p-qN (0≤m, n<1; 0<p, q<1; M+n<1; P+q≤1; The formed superlattice structure of m<p) can obtain high-dopant concentration (>1 * 10
19Cm
-3) and low-resistance n type gallium nitride contact layer.In addition, utilize each allotment formed of aluminium, indium, gallium can obtain the epitaxial that lattice constant in twos is complementary, do not chap and can not cause in the internal cause silicon heavy doping of n type gallium nitride contact layer, improve the quality of heavy blended gallium nitride contact layer, and reduce the difficulty that n type ohmic contact is made, and then can reduce the operating voltage of whole gallium nitride multiple quantum trap luminous diode greatly.
Below in conjunction with accompanying drawing, embodiment describe above-mentioned and other purpose and advantage of the present invention in detail down.
Description of drawings
Fig. 1 is lattice constant and the energy gap that shows the III-nitride material.
Fig. 2 is the structural representation according to the gallium nitride multiple quantum trap luminous diode of first embodiment of the invention.
Fig. 3 is the structural representation according to the gallium nitride multiple quantum trap luminous diode of second embodiment of the invention.
Fig. 4 is the structural representation according to the gallium nitride multiple quantum trap luminous diode of third embodiment of the invention.
Fig. 5 is the structural representation according to the gallium nitride multiple quantum trap luminous diode of fourth embodiment of the invention.Among≤the figure
10 substrates
20 resilient coatings
30 n type contact layers
40 negative electrodes
42 luminescent layers
50 p type coatings
60 p type contact layers
70 electrodes
301 have the gallium nitride based layer of silicon doping
302 have the aluminium gallium nitride alloy basic unit of silicon doping
Embodiment
Technical conceive of the present invention can be known to disclose by Fig. 1.Fig. 1 is lattice constant (Lattice Constant) and the energy gap that shows the III-nitride material.As shown in Figure 1, the lattice constant a0 of GaN (gallium nitride) is about 3.18 .Extend up and down by its lattice match line, can find to have the Al of specific composition
xIn
yGa
1-x-yN (aluminum indium nitride gallium, 0≤x, y<1, x+y≤1) has identical lattice constant and higher energy gap.
Fig. 2 is the structural representation according to the gallium nitride multiple quantum trap luminous diode of first embodiment of the invention.The structure of known gallium nitride light-emitting diode as shown in Figure 2, generally be that alumina single crystal (Sapphire) or carborundum (6H-SiC or 4H-SiC) with C-Plane or R-Plane or A-Plane is substrate 10, other material that can be used for substrate also comprises Si, ZnO, GaAs or spinelle (MgAl
2O
4), or lattice constant approaches the monocrystalline oxide of nitride-based semiconductor.Then, this structure comprises resilient coating 20 in a side of substrate 10, and this resilient coating 20 is by the aluminum indium gallium nitride Al with specific composition
1-a-bGa
aIn
bN (0≤a, b<1, a+b≤1) constitutes.On this resilient coating 20, this structure comprises n type contact layer (contact layer) 30, and the structure of this n type contact layer 30 promptly is focus of the present invention place.Be to cover the partly luminescent layer (active layer) 42 on n type contact layer 30 surfaces on this n type contact layer 30, this luminescent layer 42 is made of InGaN (InGaN).In addition, on the part that is not capped in this luminescent layer the same side and on these n type contact layer 30 surfaces, this structure also comprises negative electrode 40.
On this luminescent layer 42, this structural order piles up from lower to upper, comprises p type coating (cladding layer) 50, p type contact layer 60 respectively and covers the partly positive electrode 70 on p type contact layer 60 surfaces.The p type coating 50 that is positioned on the active luminescent layer is by there being magnesium to mix (Mg-doped), have the aluminum indium gallium nitride Al of a specific composition
1-c-dGa
cIn
dN constitutes, 0≤c, d<1, c+d≤1.Be positioned at 60 of p type contact layers on the p type coating 50 by there being magnesium to mix, have the aluminum indium gallium nitride Al of another specific composition
1-e-fGa
eIn
fN constitutes, 0≤e, f<1, e+f≤1.
As shown in Figure 2, the n type contact layer 30 of this embodiment is by multilayer, superlattice (Supperlattice) structures that the gallium nitride based layer 301 of silicon doping arranged and have the mutual stack of aluminium gallium nitride alloy basic unit 302 of silicon doping to be constituted, wherein has the energy gap of aluminium gallium nitride alloy basic unit 302 of silicon doping bigger than the energy gap of the gallium nitride based layer 301 that silicon doping is arranged.More particularly, n type contact layer 30 is to have stack one deck on the gallium nitride based layer 301 of silicon doping that the aluminium gallium nitride alloy basic unit 302 of silicon doping is arranged at one deck, and the one deck that superposes again on it has the gallium nitride based layer 301 of silicon doping, by that analogy.Perhaps, n type contact layer 30 is to have stack one deck in the aluminium gallium nitride alloy basic unit 302 of silicon doping that the gallium nitride based layer 301 of silicon doping is arranged at one deck, and the one deck that superposes again on it has the aluminium gallium nitride alloy basic unit 302 of silicon doping, by that analogy.The thickness of each gallium nitride based layer needn't be identical, but all between 20 ~200 , the growth temperature is between 600 ℃~1200 ℃.Each aluminium gallium nitride alloy Al
1-gGa
gThe composition of N (0<g<1) basic unit (that is, the parameter g in the molecular formula of prostatitis) needn't be identical, and thickness needn't be identical, but all between 20 ~200 , the growth temperature is also between 600 ℃~1200 ℃.N type contact layer 30 gross thickness comprise 50~500 layers of gallium nitride based layer 301 and aluminium gallium nitride alloy basic unit 302 altogether between 2~5 μ m, the silicon doping concentration that wherein has one deck (no matter being gallium nitride based layer 301 or aluminium gallium nitride alloy basic unit 302) at least is greater than 1 * 10
19Cm
-3Gallium nitride based layer 301 is one with the number of plies of aluminium gallium nitride alloy basic unit 302 difference identical or its number of plies.
Fig. 3 is the structural representation according to the gallium nitride multiple quantum trap luminous diode of second embodiment of the invention.As shown in Figure 3, the structure of this embodiment and first embodiment are identical, and unique difference is the material difference that n type contact layer 32 is adopted.The n type contact layer 32 of this embodiment is by multilayer, the common gallium nitride based layer 321 of mixing of indium and silicon is arranged and indium is arranged the superlattice structures that constituted with the common aluminium gallium nitride alloy basic unit of mixing of silicon 322 mutual stacks, and the energy gap of the gallium nitride based layer 321 of doping is big jointly than indium and silicon are arranged for the energy gap that the common aluminium gallium nitride alloy basic unit 322 of mixing of indium and silicon wherein arranged.More particularly, n type contact layer 32 ties up to one deck the aluminium gallium nitride alloy basic unit 322 that stack one deck has indium and silicon to mix jointly on indium and the common gallium nitride based layer 321 of mixing of silicon, the one deck that superposes again on it has indium and the common gallium nitride based layer 321 of mixing of silicon, by that analogy.Perhaps, n type contact layer 32 ties up to the gallium nitride based layer 321 that one deck has in indium and the common aluminium gallium nitride alloy basic unit 322 of mixing of silicon, stack one deck has indium and the common doping of silicon, and the one deck that superposes again on it has indium and the common aluminium gallium nitride alloy basic unit 322 of mixing of silicon, by that analogy.The thickness of each gallium nitride based layer needn't be identical, but all between 20 ~200 , the growth temperature is between 600 ℃~1200 ℃.The composition of each aluminium gallium nitride alloy basic unit needn't be identical, and thickness needn't be identical, but all between 20 ~200 , the growth temperature is also between 600 ℃~1200 ℃.N type contact layer 32 gross thickness comprise 50~500 layers of gallium nitride based layer 321 and aluminium gallium nitride alloy basic unit 322 altogether between 2~5 μ m, wherein have the indium of one deck (no matter being gallium nitride based layer 321 or aluminium gallium nitride alloy basic unit 322) and silicon doping concentration at least greater than 1 * 10
19Cm
-3Gallium nitride based layer 321 is one with the number of plies of aluminium gallium nitride alloy basic unit 322 difference identical or its number of plies.
Fig. 4 is the structural representation according to the gallium nitride multiple quantum trap luminous diode of third embodiment of the invention.As shown in Figure 4, the structure of this embodiment and first and second embodiment are identical, and unique difference is the material difference that n type contact layer 34 is adopted.The n type contact layer 34 of this embodiment is by multilayer, the common aluminium gallium nitride alloy basic unit 341 of mixing of indium and silicon is arranged and indium is arranged the superlattice structures that constituted with the common aluminium gallium nitride alloy basic unit of mixing of silicon 342 mutual stacks, and the energy gap of the aluminium gallium nitride alloy basic unit 341 of doping is big jointly than indium and silicon are arranged for the energy gap that the common aluminium gallium nitride alloy basic unit 342 of mixing of indium and silicon wherein arranged.More particularly, n type contact layer 34 is at one deck the aluminium gallium nitride alloy basic unit 342 that stack one deck has indium and silicon to mix jointly in indium and the common aluminium gallium nitride alloy basic unit 341 of mixing of silicon to be arranged, the one deck that superposes again on it has indium and the common aluminium gallium nitride alloy basic unit 341 of mixing of silicon, by that analogy.Perhaps, n type contact layer 34 is at one deck the aluminium gallium nitride alloy basic unit 341 that stack one deck has indium and silicon to mix jointly in indium and the common aluminium gallium nitride alloy basic unit 342 of mixing of silicon to be arranged, and the one deck that superposes again on it has indium and the common aluminium gallium nitride alloy basic unit 342 of mixing of silicon, by that analogy.The thickness of each aluminium gallium nitride alloy layer needn't be identical, but all between 20 ~200 , the growth temperature is between 600 ℃~1200 ℃.The composition of adjacent aluminium gallium nitride alloy basic unit is inequality, but the composition of non-conterminous aluminium gallium nitride alloy basic unit can be identical, also can be inequality, and each layer thickness needn't be identical, but all between 20 ~200 , the growth temperature is also between 600 ℃~1200 ℃.N type contact layer 34 gross thickness are between 2~5 μ m, comprise 50~500 layers of aluminium gallium nitride alloy basic unit 341 and aluminium gallium nitride alloy basic unit 342 altogether, wherein have the indium of one deck (no matter being aluminium gallium nitride alloy basic unit 341 or aluminium gallium nitride alloy basic unit 342) and silicon doping concentration at least greater than 1 * 10
19Cm
-3Aluminium gallium nitride alloy basic unit 341 is one with the number of plies of aluminium gallium nitride alloy basic unit 342 difference identical or its number of plies.
Fig. 5 is the structural representation according to the gallium nitride multiple quantum trap luminous diode of fourth embodiment of the invention.As shown in Figure 5, structure and the previous embodiment of this embodiment are identical, and unique difference is the material difference that n type contact layer 36 is adopted.The n type contact layer 36 of this embodiment is by multilayer, the superlattice structures that the aluminum indium nitride gallium basic unit 361 of silicon doping arranged and have the mutual stack of aluminum indium nitride gallium basic unit 362 of silicon doping to be constituted, wherein has the energy gap of aluminum indium nitride gallium basic unit 362 of silicon doping bigger than the energy gap of the aluminum indium nitride gallium basic unit 361 that silicon doping is arranged.More particularly, n type contact layer 36 ties up to one deck has stack one deck in the aluminum indium nitride gallium basic unit 361 of silicon doping that the aluminum indium nitride gallium basic unit 362 of silicon doping is arranged, and the one deck that superposes again on it has the aluminum indium nitride gallium basic unit 361 of silicon doping, by that analogy.Perhaps, n type contact layer 36 is to have stack one deck in the aluminum indium nitride gallium basic unit 362 of silicon doping that the aluminum indium nitride gallium basic unit 361 of silicon doping is arranged at one deck, and the one deck that superposes again on it has the aluminum indium nitride gallium basic unit 362 of silicon doping, by that analogy.The thickness of each aluminum indium nitride gallium basic unit needn't be identical, but all between 20 ~200 , the growth temperature is between 600 ℃~1200 ℃.The composition of adjacent aluminum indium nitride gallium basic unit is inequality, but the composition of non-conterminous aluminum indium nitride gallium layer can be identical, also can be inequality, and each layer thickness needn't be identical, but all between 20 ~200 , the growth temperature is also between 600 ℃~1200 ℃.N type contact layer 36 gross thickness are between 2~5 μ m, comprise 50~500 layers of aluminum indium nitride gallium basic unit 361 and aluminum indium nitride gallium basic unit 362 altogether, the silicon doping concentration that wherein has one deck (no matter being aluminum indium nitride gallium basic unit 361 or aluminum indium nitride gallium basic unit 362) at least is greater than 1 * 10
19Cm
-3Aluminum indium nitride gallium basic unit 361 is one with the number of plies of aluminum indium nitride gallium basic unit 362 difference identical or its number of plies.
In this embodiment, form different aluminum indium nitride gallium Al by making up two kinds
mIn
nGa
1-m-nN and Al
pIn
qGa
1-p-qN (0≤m, n<1; 0<p, q<1; M+n<1; P+q≤1; M<p) formed superlattice structure can obtain high-dopant concentration (>1 * 10
19Cm
-3) and low-resistance n type gallium nitride contact layer.In addition, utilize each allotment formed of aluminium, indium, gallium can obtain the epitaxial that lattice constant in twos is complementary, do not chap and can not cause in the internal cause silicon heavy doping of n type gallium nitride contact layer, improve the quality of heavy blended gallium nitride contact layer, and reduce the difficulty that n type ohmic contact is made, and then can reduce the operating voltage of whole gallium nitride multiple quantum trap luminous diode greatly.
Foregoing only is preferred embodiment of the present invention, should not limit scope of the invention process with this, and every equalization of doing according to scope of the present invention changes with revising and all should belong in the scope that the present invention contains.