CN1230923C - Light-emitting diode structure - Google Patents
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- CN1230923C CN1230923C CNB021285136A CN02128513A CN1230923C CN 1230923 C CN1230923 C CN 1230923C CN B021285136 A CNB021285136 A CN B021285136A CN 02128513 A CN02128513 A CN 02128513A CN 1230923 C CN1230923 C CN 1230923C
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Abstract
The present invention relates to a light-emitting diode structure, particularly to a light-emitting diode made from compound semiconductor materials. Light is emitted from the active zone of a multiple quantum well structure; the active zone is wrapped by an upper InGaAlP layer, a lower InGaAlP layer and an upper wrapping layer in a sandwich state. The light-emitting efficiency of the active zone can be strengthened by increasing light rays and electron reflecting layers in the light-emitting diode. The epitaxial layer of the InGaAlP is generated on a thin GaAs substrate by an organic metal vapor phase epitaxial (OMVPE) method to improve the quality of the epitaxial layer and the smoothness and the light-emitting efficiency of an epitaxial surface, wherein the substrate has good assembly feasibility, high brightness and A.
Description
Technical field
The present invention relates to a kind of semiconductor LED structure, particularly a kind of at thin suprabasil semiconductor light-emitting-diode assembly.
Background technology
Light-emitting diode (LED; Light emitting diode) be widely used in the different fields, as light source in order to reduce electrical source consumption, high efficiency and high reliability.More particularly, combined type semiconductor such as GaP (green wavelength), GaAsP (yellow, orange or red wavelength) and GaAlAs (red wavelength) are widely used in the material of the light-emitting diode of visible wavelength range.
Yet the luminous efficiency of each GaP and GaAsP is the semi-conducting material of indirect shape, even utilize transparent substrates as the influence of eliminating light absorption, its luminous efficiency approximately is to be lower than 0.5%.In others, influence luminous efficiency and be indirect turnover state in short wavelength range.For example, when visible wavelength was 635nm, its luminous efficiency was about 1%.
Combined type semiconductor mixed crystal does not comprise nitride (nitride) in three-five families (III-V), the InGaAlP mixed crystal demonstrates the maximum energy rank band of indirect turnover kenel, and its absorbing light ability can be 0.5 to 0.6 micron (micron) as its luminous wavelength of luminescence component.In particular, light-emitting diode comprises GaAs substrate and InGaAlP layer, and its lattice coefficient is in alignment with the GaAs substrate, and structure can be launched green glow to red light wavelength under high brightness thus.Yet at the light-emitting diode of this type, its optical efficiency remains not enough in short wavelength range.
With reference to the schematic diagram of figure 1 for the traditional light-emitting diodes structure 100 of expression.In this figure, light-emitting diode component structure 100 comprises and has tetrahedron In
0.5(Ga
1-xAl
x)
0.5P alloy system and the two-phase heterostructure (DH that in n-GaAs substrate 102, forms; Double hetero-structure), wherein the thickness of n-GaAs substrate 102 is about 350 microns (um).In traditional light-emitting diode 102, the problem of substrate thickness for considering.Generally speaking, GaAs substrate 102 is directly bought from manufacturer and is obtained, and utilize mode that a preliminary processes (pre-process) grinds GaAs substrate 102 utilization or etching that the thickness of GaAs substrate 102 is ground to the thickness that is fit to as the light-emitting diode substrate, as 180 microns.Yet, no matter be to grind or etch process, the reliability of back its base material of the consistency of GaAs substrate 102 and process preliminary processes can influence the luminous efficiency of whole light-emitting diode after forming.In addition, the temperature of GaAs substrate 102 also can't be kept consistency because the thickness of substrate 102 is too high, so that form in the process of substrate 102 in extension, cause substrate 102 to have the temperature difference to exist up and down, this temperature that gets substrate 102 is more uncontrollable, makes the luminous efficiency of light emitting diode construction 100 reduce.
Then, be with reference to figure 1 equally, have light-emitting diode 100 that the p-n of preceding bias voltage (forward bias) connects face by injected hole (hole) among p type coating layer (the p-type cladding layer) 108, electronics is injected with in the source region by n-type (n-type) coating layer 104.Its active layer (active layer) visible emitting is owing to electronics and the hole reason of combination more again in active region.Inject electronics and hole as minority carrier pass active area and electronics, hole again in conjunction be by luminous again in conjunction with or non-luminous combination again.Emission wavelength based on the light emitting diode construction 100 of InGaAlP can be by changing In in active layer
0.5(Ga
1-xAl
x)
0.5The amount of P alloy aluminum composition is adjusted, and InGaAlP is that main light-emitting diode 100 has suitable being with to assemble distinctive emission wavelength.For example, as the ruddiness or the short wavelength of yellow-green light, the concentration of its aluminium composition is wanted higher and is produced luminous.In addition, because the relation of low carrier density makes the thickness of active layer 106 can reduce at active area.Active area is used for carrier injection and charge carrier again in conjunction with producing light, and the thickness of general active area is approximately 0.3 to 0.5 micron.In order to obtain higher luminous efficiency, be positioned at the then requirement to some extent of the needed material quality of active area.This requirement promptly is the concentration that the impurity on active area can reduce non-radiative recombination center.
In general, In
0.5(Ga
1-xAl
x)
0.5P active layer 106 is a undoped layer, and it electrically can be n or p type, and its doping content is about 5*10
15To 1*10
17Every square centimeter.With regard to others, the degree of mixing at active layer 106 is along with the content of aluminium composition in active area increases and increases.This is owing to higher aluminum concentration in active area is to cause the composition of impurity to increase.For the short wavelength, it is relevant with the reduction of radiative internal quantum efficiency in the concentration of active area to increase aluminium.As previously discussed, the aluminium of higher concentration increases to cause non-luminous be combined in again in the luminescent layer along with increasing dark plane at active area, and makes luminous efficiency and reduce.
N type (104) or p type (108) coating layer provide the source of an injection charge carrier and have one and can be higher than active area with restriction injection charge carrier and luminous in rank.These coating layers 104,108 need good electrical conductivity and reach suitable doping content for entering active area to obtain a high luminous efficiency for enough injection charge carriers.And at In
0.5(Ga
1-xAl
x)
0.5The P layer should have enough thickness preventing being back to coating layer at the charge carrier of active area, but In
0.5(Ga
1-xAl
x)
0.5The thickness low LCL of P layer then can have influence on the luminous efficiency of whole light-emitting diode 100.Therefore, most injection charge carrier can overflow enter coating layer, and meeting causes the phenomenon generation of leakage current owing to the non-photism reorganization of the charge carrier of these overflows.So the luminous efficiency that comprises the two-phase heterostructure at traditional light-emitting diode 100 shortens along with the wavelength of assembly and reduces.
Behind p type coating layer 108, form as the electric current dispersion layer (current spreading layer) 110 that disperses luminous efficiency.Electric current dispersion layer 110 need penetrate into semi-conducting material by active area with emission wavelength.In addition, a window layers (window layer) 112 effectively scattered current enters active layer 106 and coating layer, and doping content that window layers 112 need be high and the enough thickness of needs.Then a Metal Contact (metalcontact) 114 is arranged above window layers 112, being positioned at GaAs substrate 102 belows also has a Metal Contact 116.
According to the above, can know in traditional light-emitting diode 100 because the thickness of GaAs substrate 102 for one of the main cause of the whole lumination of light emitting diode efficient of influence, is being more difficult to get gold-tinted and the green glow with high-luminous-efficiency in addition in the light-emitting diode 100 of traditional InGaAlP series.
Summary of the invention
Main purpose of the present invention is to overcome the deficiencies in the prior art and defective, a kind of thin thickness is provided and (miscut) angle of cutting sth. askew towards＜111 the A face, its mis-cut angle greater than 10 the degree angles the GaAs substrate to keep the consistency of base reservoir temperature.
A further object of the present invention is to improve the reliability of whole light-emitting diode component to increase assembly quality and luminosity.
Another object of the present invention is to save the technology that forms light-emitting diode component.
Another purpose of the present invention is to improve the temperature gradient of whole GaAs substrate to increase the radiating efficiency of light-emitting diode.
According to above-described purpose, the invention provides a kind of light emitting diode construction with thin layer GaAs substrate.This structure comprises thin GaAs substrate and has a mis-cut angle and tend to＜111〉A faces, and one is used to improve GaAs substrate surface flatness and conforming resilient coating (Buffer layer) is positioned at GaAs substrate, a decentralized Bragg reflecting layer (DBR; Distributed Bragg Reflector) be positioned at resilient coating top and be positioned on the decentralized Bragg reflecting layer by emission light, the lower floor's coating layer (lower cladding layer) that active area (activeregion) conduction comes in order to reflection, its effect is charge carrier (carrier) injection to be entered active area and charge carrier is confined in the active area.Then, a multiple quantum trap layer (MQW; Multi-quantumwells) be positioned at lower floor coating layer top, this layer is to be used for replacing traditional active layer and in short wavelength's light emitting region, to increase the efficient and the content of minimizing aluminium in multiple quantum trap of active layer.In addition, the multiple quantum trap layer can increase the luminous efficiency of light-emitting diode.A upper layer packets coating (upper cladding layer) is positioned at the multiple quantum trap top then, this upper layer packets coating be used for that carrier injection entered active area and with carrier confinement in active area, wherein lower floor's coating layer is opposite with the conductivity of upper layer packets coating.Then, one current barrier layer (currentblocking layer) is positioned at the top of upper layer packets coating, its function is to be used for forming on a vertical plane the path of a low resistance to inject charge carrier, has a window layers (window layer) to disperse to use as electric current in light-emitting diode in electric current dispersion layer (current spreadinglayer) top then.There is being a Metal Contact (metal contact) that a Metal Contact is arranged below the GaAs substrate above the window layers then.
In light emitting diode construction of the present invention, because the thin thickness of GaAs substrate, make that in the process of epitaxial growth its temperature difference is very for a short time to be easy to control formation temperature, and the consistency of its material and reliability also can increase the luminosity that therefore increases light-emitting diode; In addition owing to the thin thickness that forms, so can significantly simplify in the technology of utilizing grinding or etching mode that the thickness that is applicable to light emitting diode construction is worn in the GaAs substrate.
Description of drawings
Fig. 1 by according to tradition the schematic diagram of light emitting diode construction of exposure technology;
Fig. 2 is disclosed technology according to the present invention, the schematic cross-section of light emitting diode construction;
Fig. 3 is disclosed technology according to the present invention, the schematic cross-section of light emitting diode construction.
Symbol description among the figure
10 light emitting diode constructions
12 GaAs substrates
14 resilient coatings
16 decentralized Bragg reflecting layers
18 n type lower floor coating layers
20 multi layer quantum wells
22 p type upper layer packets coating
24 intermediate barrier layers
26 current barrier layers
28 window layers
30 Metal Contact
32 Metal Contact
50 light emitting diode constructions
52 GaAs substrates
54 resilient coatings
56 decentralized Bragg reflecting layers
58 n type lower floor coating layers
60 strain multiple quantum traps
62 electron reflection layers
64 p type upper layer packets coating
Strain barrier layer in the middle of 66
68 current barrier layers
70 window layers
72 Metal Contact
74 Metal Contact
100 light emitting diode constructions
102 GaAs substrates
104 n type lower floor coating layers
106 active layers
108 p type upper layer packets coating
110 electric current dispersion layers
112 window layers
114 Metal Contact
116 Metal Contact
Embodiment
Some embodiments of the present invention can be described in detail as follows.Yet except describing in detail, the present invention can also be widely implements at other embodiment, and scope of the present invention do not limited, and its scope with claims is as the criterion.
Based on the light-emitting diode of InGaAlP, its glow color can be by changing In
0.5(Ga
1-xAl
x)
0.5The composition of P alloy in active layer adjusted, and has suitable energy gap to assemble special emission wavelength.In in active area
0.5(Ga
1-xAl
x)
0.5Orderliness (order) structure of tending to the P alloy causes at energy gap width (width of the band gap) and reduces.Aluminium in active area needs higher content to reach identical wavelength of transmitted light, still can cause the high impurity density in active area and cause low emission efficiency.The origin of orderliness structure similarly is in the semiconductive thin film, and atom can be led because of in the static displacement (static displacement) of atom with the order or the change of composition, thereby is created in the localized variation in the deformation of lattice tetrahedron.At In
0.5(Ga
1-xAl
x)
0.5In the P alloy system, indium (In; Indium) have than gallium (Ga; Gallium) or aluminium (Al; Aluminum) atom has bigger tetrahedron covalent radius.Therefore, the otherness of tetrahedron covalent radius can produce similar gathering.As a result, relatively producing the crystal structure local deformation shrinks and prolongation.The viewpoint of decomposing thermodynamics (spinodal decompositionthermodynamic) by spinodal, in phasor (phase diagram), under a transition temperature (transition temperature), have the turnover state of an orderliness (order) to (disorder) out of order.By considering that experiment and difference on the thermodynamic argument are that kinetic energy and surface texture order form.Experiment by us can be known In
0.5(Ga
1-xAl
x)
0.5The P film is followed spinodal and is decomposed the thermodynamics basic principle, long brilliant temperature be 660 ℃ to 770 ℃ between tend to certain order structure in various degree.And the temperature that light-emitting diode is grown up is higher than 700 ℃ of epitaxial growth temperature.
With regard on the other hand,＜001〉GaAs growth again is＜110〉the side surface layer of direction has changeability compression and the zone of extending.Because indium has than gallium or aluminium has bigger tetrahedron covalent radius, the changeability on growth face prolongs and compressibility, is the suitable nucleation site of energy, for individual other indium, gallium or aluminium atom, extremely is fit to their growth.This point hinting, except above-mentioned orderliness with do not have the transition temperature of order, the formation of orderliness structure is relevant with the surface texture of substrate.By our experiment, degree can be improved by the GaAs substrate of using different mis-cut angles orderly.Orderliness and transition temperature out of order are to descend because of the increase of substrate GaAs cutting angle.On the surface of cutting sth. askew the GaAs substrate, periodically extend and the resurfacing zone of shrinking, can be improved by the increase of substrate GaAs mis-cut angle.Can know that by above result along with the increase of the mis-cut angle of GaAs substrate, the atom sequence rule degree in InGaAlP can reduce significantly.
In addition, in order to increase the luminous efficiency of light-emitting diode integral body, except the GaAs substrate is grown up＜110〉the surface of A, when general GaAs substrate is obtained by manufacturer thickness be approximately 350 microns, and then utilize and grind or etched mode, substrate is ground to the thickness that is appropriate to as the light-emitting diode substrate, generally is approximately 180 microns.But, be etched to 180 microns by 350 microns of thickness, need the more technology cost of cost; Therefore, in most preferred embodiment of the present invention, employed GaAs substrate thickness is 150 to 250 microns, optimum thickness is 210 microns, the advantage that forms the GaAs substrate of this thickness range is that the needed technology cost of formed thinner thickness reduces, and can form the GaAs substrate of more amount in same technology; In addition, when being ground to 180 microns, employed etching or grinding technics also can be simplified significantly, and can obtain needed substrate thickness soon; Moreover when the mode of utilizing extension formed the GaAs substrate of this thickness, its formation temperature can have good control, made that the temperature gradient between the substrate does not up and down have too big variation, and can obtain the good substrate of a reliability.In addition, have also preferablely, make its luminous efficiency also can increase than its thermal diffusivity of substrate of minimal thickness.In addition, has more conforming radiating efficiency when above the GaAs substrate, forming film, therefore the luminous efficacy that can improve the thermolysis of light-emitting diode and increase whole light-emitting diode.
Under a certain growth temperature, In
0.5(Ga
1-xAl
x)
0.5Regular texture is regarded as reducing a factor of quantum efficiency in the P alloy system.Therefore, must increase aluminium at In
0.5(Ga
1-xAl
x)
0.5The composition of P active area, obtain specific can rank the quantum well of width, therefore, can be by In
0.5(Ga
1-xAl
x)
0.5The P epitaxial growth is cut sth. askew in the substrate one, and makes transition temperature reduce and be lower than 700 ℃.
In addition, the In that contains aluminium
0.5(Ga
1-xAl
x)
0.5Quantum efficiency in the P multiple quantum trap can be by the mis-cut angle that increases substrate, and is improved.Cutting sth. askew of GaAs substrate more towards＜111〉the A surface, can expose cation terminal step edges (cation terminated step edges) the more.Incorporating of impurity of absorption is via a stepped trap (step traps), and relevant with the bond shape between the terminal ladder with the lip-deep absorption impurity of growing up.Cation stops step edges to be had a single bond and more weak absorption position is provided.Therefore, ladder like trap effect (step trappingefficiency) can along with the surface of growing up along＜111 the mis-cut angle of A increases and reduces its adhesion effect.So the adding of active region impurity (for example silicon or oxygen) will reduce along with the increase of mis-cut angle.These foreign bodys can be used as the deep layer of light emitting area and the center of non-luminous combination again, and influence the emission effciency of light-emitting diode.Among the present invention, being that substrate and mis-cut angle are along person＜111 with GaAs〉A is greater than 10 degree angles, and its best mis-cut angle is 15 degree angles, and the light that is regarded as being launched has preferable efficient.
In addition, can cut sth. askew substrate GaAs structure and be improved by being formed on one based on the film smoothness of the light-emitting diode of InGaAlP and quality.Be used in the past improving applied epitaxy technology of semi-conductive surface smoothness such as liquid phase epitaxial method (Liquid Phase Epitaxy, LPE) or vapour phase epitaxy method (Chemical Vapor Deposition is CVD) to improve the smoothness of film.Among the present invention, then be based on the light-emitting diode of InGaAlP and use organic metal vapour phase epitaxy method (Organometalic Vapor Phase Epitaxy, OMVPE) length is formed in the GaAs substrate in the angles of mis-cut angle greater than 10 degree, improves the film surface smoothness.Learn in the research by us, the smoothness of light emitting diode construction can increase along with the increase of substrate mis-cut angle, and the improvement of this smoothness is that main epitaxial growth is obvious especially in the GaAs substrate for three-five families non-coupling (mismatch) dissimilar structure such as GaP, AlGaP and InGaAlP.The unmatched degree of lattice between these epitaxial loayers such as GaP, AlGaP and InGaAlP alloy and substrate is approximately 0-3.6%, and relevant with the composition of alloy.
In the deposition process, the growth of film initial stage tends to grow the crystal of some shapes such as island in substrate in non-coupling substrate, and the size of these islands is along with the non-matching degree of film and substrate increases and increases.This will cause forming highdensity wire difference row (threaddislocation) on the film, and increase the surface roughness of deposit film.These highdensity crystal defects and coarse film surface can be counted out and reduce tuberculosis island area and do a gradient (gradient) in the lattice constant of non-matching heterogeneous structure and change and be improved by increasing surface crystallization.Film tuberculosis is counted out to be increased and the reducing of island area, and is another emphasis of claim in the present invention.Can use the GaAs substrate and cut sth. askew one, and be inserted into light-emitting diode In with an InGaAlP intermediate layer greater than 10 degree angles
0.5(Ga
1-xAl
x)
0.5Reach this effect as gradient layer between P epitaxial loayer and window layers.In the substrate of cutting sth. askew, the substrate step edges can increase and increase along with the substrate mis-cut angle.These step edges provide the nucleation site of a low energy position to deposit film.Therefore, density is higher and island tuberculosis that area is less can cause membrane quality in the substrate of cutting sth. askew increase with reach more level and smooth degree, and the change of membrane quality can increase the delivery efficiency of lumination of light emitting diode.
In addition, the smoothness of film surface can increase the scope of component process, the state space (process window of device fabrication) made of the efficient of the quality of the metallic contact manufacturing of light-emitting diode and encapsulation, film, luminous element, assembly for example is by In in the growth light-emitting diode
0.5(Ga
1-xAl
x)
0.5P foundation structure is in mis-cut angle 10 degree angles or above GaAs substrate.
With reference to the schematic diagram of figure 2 for the expression light emitting diode construction.According to advantage described above, in Fig. 2, the structure of its light-emitting diode 10 comprises a reflection layer and a tetrahedron alloy In at least
0.5(Ga
1-xAl
x)
0.5P is long to tilt (n-type misoriented) above the GaAs substrate 12 in the n type.And light-emitting diode 10 is by 14, one n type AlAs/Al of a n type GaAs resilient coating (buffer layer)
xGa
1-xAs-or In
0.5(Ga
1-xAl
x)
0.5P is main decentralized Bragg reflecting layer (DBR; Distributed Bragg reflector) 16, one n type In as first coating layer
0.5(Ga
1-xAl
x)
0.5Assorted In is not oozed in P lower floor coating layer (cladding layer) 18, one strains (strain)
y(Ga
1-xAl
x)
1-yP/In
0.5(Ga
1-xAl
x)
0.5P multiple quantum trap (MQW; Multiplequantum well) 20, one p-type In0 as second coating layer
.5(Ga
1-xAl
x)
0.5The In that P upper layer packets coating 22, approaches
0.5(Ga
1-xAl
x)
0.5P intermediate barrier layers (intermediate barrier layer) 24, one p-type GaP or AlGaAs current barrier layer (current blocking layer) 26, one window layers (window layer) 28, contact 32 with a underlying metal as a top-level metallic of the first metal layer contact (metalelectrode contact) 30.
In most preferred embodiment of the present invention, utilize multiple quantum trap 20 to replace traditional active layer 106 (as shown in Figure 1).Has n type AlAs/Al
xGa
1-xAs-, AlAs/In
0.5(Ga
1-xAl
x)
0.5P-or In
0.5(Ga
1-xAl
x)
0.5P is that the light antireflecting layer of main decentralized Bragg reflecting layer 16 is used for reverberation and is positioned at In
0.5(Ga
1-xAl
x)
0.5P is the bottom of master's light emitting diode construction 10.In addition, an In
0.5(Ga
1-xAl
x)
0.5P be main barrier layer 26 insert p type coating layers 20 and window layers 28 between and a Metal Contact 30 32 of another Metal Contact of top being positioned at window layers 28 be the below that is positioned at GaAs substrate 12.
Light emitting diode construction 10 is long to have about 0.2 to the 0.4 micron silicon of one deck to ooze that assorted GaAs resilient coating 14 is long to be oozed on the assorted inclined substrate at silicon in Fig. 2.GaAs resilient coating 14 is to be used for improving GaAs substrate 10 lip-deep flatness of growth and uniformities.Growth GaAs resilient coating 14 is necessary for the preferable quality of the heterogeneous interface of the multiple quantum trap of light-emitting diode 10 (hetero-interfaces) film.Then GaAs resilient coating 14 after, a decentralized Bragg reflecting layer 16 is located at above the GaAs resilient coating 14 so that the light reflection to be provided.The material of making in this layer light reflector 16 is to be selected from forbidding and forming with the material that active area is similar to very much by rank band height (prohibited bandheight) of energy rank.What the selection that this layer 16 made material need be considered the difference of lattice match (lattice matching), energy gap band and reflection coefficient and indivedual reflector oozes the assorted limit (doping limit of individual reflecting layer).Generally speaking, the cycle of one ten to 20 Bragg reflecting layer 16 can increase 1.5 times of light external quantum efficiency (external quantum efficiency of emitting light) to general light-emitting diode but do not use under the situation of Bragg reflecting layer 16.AlAs/Al
xGa
1-xThe wavelength X of the reflected wave of As Bragg reflecting layer 16 is decided by the thickness in indivedual reflector, and its functional relation the following is d=λ/4n, and wherein n is the reflection coefficient of Bragg reflecting layer 16 each layers.The purpose of Bragg reflecting layer 16 is to be used for reflecting the incident ray of being come in by active area, Al
xGa
1-xThe energy gap of As must be greater than the energy gap of active area to prevent the absorption of any light.In addition, must strengthen as much as possible with the preferable reflection efficiency again of acquisition Bragg reflecting layer 16 in the layer of Bragg reflecting layer 16 each layers difference with layer reflection coefficient.But Bragg reflecting layer 16 is also being played the part of need need high density (〉=2*10
17/ cm
2) the electric current of conduction carrier inject the function of transfer layer.
Because the n-type oozes the intrinsic limitation (intrinsic limitation) of assorted concentration in the Bragg reflecting layer 16 of AlAs-substrate, the restriction of Bragg reflecting layer 16 is to reach a low forward operation bias voltage and to obtain in the Bragg reflecting layer 16 reflectivity simultaneously more than or equal to the efficient of 90-95%.Generally speaking, the cycle based on the Bragg reflecting layer 16 of InGaAlP-is approximately between ten to 20.The standby element of another Bragg reflecting layer 16 is In
0.5(Ga
1-xAl
x)
0.5The P-base alloy, it can reach higher electrical conductivity than Bragg reflecting layer 16 substrates of AlAs/AlGaAs-substrate, and still, it has but been offset by growth the controlled of lattice match in GaAs substrate 12.
In Fig. 2, n-type lower floor coating layer 18 is to be used for supplying with charge carrier to be injected with the source region and charge carrier is confined to active area.The molecular composition of aluminium is greatly between 0.7 to 1 in the n-type lower floor coating layer 18, and relevant system with the radiation wavelength of active area.The thickness of n-type lower floor coating layer 18 must come thickly than the diffusion length of charge carrier, is diffused into n type lower floor coating layer 18 to avoid charge carrier by active area.
At In
0.5(Ga
1-xAl
x)
0.5The n type in the P or the doping content scope of p type cause that efficient electronics is necessary with luminiferous the combination again in hole in active area.The overflow meeting of any indivedual injection charge carriers because the position deviation that p-n connects face with ooze the molecule of mixing and cause non-emission to combine the generation at (non-radiative recombination) center again in the diffusion inside of active area, and cause the minimizing of the efficient of radiating light.
And then behind n type lower floor coating layer 18, the In of a strain
y(Ga
1-xAl
x)
1-yP/In
0.5(Ga
1-xAl
x)
0.5P multiple quantum trap 20 is worked as active layer in the middle of inserting n type (lower floor) 18 and p type (upper strata) coating layer 22.Most preferred embodiment in the present invention is to be the efficient and the content that reduces aluminium in the quantum well that the multiple quantum trap 20 of superlattice (superlattice) is used for increasing active layer with InGaAlP.Quantum well structure can increase the efficient of radiating light in light-emitting diode 10.Quantum well is formed by the resistance barrier (barrier with a higher band gap) of a narrow band gap " well " with a higher energy gap.As a result, the energy in electronics and hole is quantized (limitation) and can not moves freely in the electric current incident direction.But still can on the vertical plane of incident current, move freely and combination again.At multiple quantum trap In
y(Ga
1-xAl
x)
1-yP/In
0.5(Ga
1-xAl
x)
0.5Among the P 20, in the conduction band, urge conductive strips can rank upwards, and the charge carrier that is confined to valence band urges valence band can rank downward.Multiple quantum trap structure 20 can move effective wavelength to a shorter wavelength of (shift) radiating light.Therefore, the content of aluminium can reduce in a large number in the active area, makes that the multiple quantum structure of light-emitting diode 10 will increase the lifetime of non-radiative reorganization for a specific radiating light source wavelength, and reduces being absorbed of light radiation.
Therefore, multiple quantum trap structure 20 has reduced aluminium content, and the charge carrier lifetime of combination has also shortened again in radiation.Therefore, light-emitting diode 10 its quantum efficiencies with multiple quantum trap 20 active areas can roll up.Between 0 to 0.3, between green-gold-tinted, it adjusts with the thickness of person's quantum well and the number of quantum well corresponding wavelength the composition of the aluminium of alloy between ruddiness greatly in the multiple quantum trap 20.Aluminium is formed the alloy In of direct gap in multiple quantum trap 20
0.5(Ga
1-xAl
x)
0.5P, the wavelength of transmitted light of multiple quantum trap 20 and the thickness of well have great association.
When the thickness of multiple quantum trap 20 reduces, its conductive strips quantization charge carrier will effectively secondaryly can be with (sub-band) up to push away, and covalency band quantization charge carrier can be taken to down effective pair and pushes away.The quantization band structure of multiple quantum trap 20 well thick about 1 to 10 micron quite responsive.As a result, because the quantization of energy stage structure, wavelength can shorten when electronics combined with the hole again.In
0.5(Ga
1-xAl
x)
0.5Between 1 to 10 micron, the optimal luminescent efficient cycle is 10 to 50 to the general gross thickness of P alloy greatly.On the other hand, luminous internal quantum is also relevant to (well/resistance) thickness ratio that is jammed with well.General efficient charge carrier again in conjunction with the time, well and the ratio that is jammed are greatly between 0.75 to 1.25.
With reference to figure 3, expression one has multiple quantum resistance barrier (MQB; Multi-quantum barrier) light-emitting diode 50 structures.In one embodiment wherein of the present invention, light emitting diode construction 50 is by the GaAs resilient coating 54 that is positioned at n-type inclination GaAs substrate 52, be positioned at the decentralized Bragg reflecting layer 56 of GaAs resilient coating 54 tops, be positioned at the n type lower floor coating layer 58 of decentralized Bragg reflecting layer 56 tops, be positioned at the strain multiple quantum trap 60 of n type lower floor coating layer 58 tops, be positioned at the electron reflection layer (electronreflector) 62 of strain multiple quantum trap 60 tops, be positioned at the p type upper layer packets coating 64 of electron reflection layer 62 top, be positioned at the thin strain intermediate barrier layers In of p type upper layer packets coating 64 tops
0.5(Ga
1-xAl
x)
0.5 P 66, the p type GaP that is positioned at intermediate barrier layers 66 tops or p type AlGaAs current barrier layer (currentblocking layer) 68, be positioned at the window layers 70 of electric current dispersion layer 68 tops, 74 formations of lower metal contact that are positioned at the Metal Contact 72 of light-emitting diodes structure 50 tops and are positioned at GaAs substrate 52 belows.
In most preferred embodiment of the present invention, a thin strain intermediate barrier layers 66 is inserted into p-type upper layer packets coating 64 tops to increase the resistance barrier height (barrierheight) of p type upper layer packets coating 64.Electron reflection layer 62 is to grow up with the organic metal vapour phase epitaxy method equally, and needs interface contrast very accurately, the thickness of layer and the accurate control of composition.In addition, thin strain intermediate barrier layers 66 have one can its size of rank be equal to or greater than p type upper layer packets coating 64 can rank, and the zone that is positioned near active layer 60 enters p type upper layer packets coating 64 to improve the luminous efficiency of light-emitting diode 50 to prevent charge carrier by the active area overflow.And p-type In
0.5Al
0.5P electron reflection layer 62 is strain (strained), and its position has suitable thickness and stress electrons tunnel (tunneling) effect to prevent to be produced by active area near active area.Because In
0.5(Ga
1-xAl
x)
0.5P/In
0.5Al
0.5The cycle of P superlattice increases, and when the light ejaculation efficient of active area also increased, this was because the reason that the reflectivity of electron reflection layer 62 increases.
Yet this phenomenon is in the thickness of individual other electron reflection layer 62 is 2 to 5 millimeters scope, and is obvious especially when having gradient (gradient) or interim (step) thickness to increase, the In in multilayer electronic reflector 62
0.5(Ga
1-xAl
x)
0.5The varied in thickness of P (gradient), expression is by the different reflected energies that inject high-energy electron of active area, therefore, charge carrier is confined to gradient or ladder like the zone and obtain high electron impact energy, and the diversity of electron reflection layer 62 (variety inelectron reflector) can be obtained by the gradient variation of the thickness of layer.In most preferred embodiment, electron reflection layer 62 comprises a strain barrier layer, and the In near active layer 60 is then arranged
0.5(Ga
1-xAl
x)
0.5P/In
0.5Al
0.5The overflow charge carrier that the super crystal structure layer of P is come by active area with reflection.
Next, above multiple quantum trap 60 and electron reflection layer 62, be a p-type upper layer packets coating 64.P-type upper layer packets coating 64 is to be used for charge carrier is injected into active area, and the charge carrier limitation is stayed active area.The thickness of p-type upper layer packets coating 64 must enter p type upper layer packets coating 64 with the charge carrier that prevents active area greater than the diffusion length of injecting charge carrier.In addition, p type upper layer packets coating 64 must be thicker than n type lower floor coating layer 58, and its reason is because the diffusible relation that the p type oozes assorted element such as Zn atom or Mg atom in the developmental process of light-emitting diode 50.One typical p-type upper layer packets coating 64 thickness are greatly between 0.5 to 1.5 micron.
Then be that one deck oozes the thin In of assorted density greater than p-type upper layer packets coating 64 above p-type upper layer packets coating 64
0.5(Ga
1-xAl
x)
0.5 Strained layer 66 in the middle of the P, strained layer 66 was to be used for guaranteeing to inject charge carrier can pass and scatter in the middle of this was thin, and for guarantee this thin in the middle of high conductance of strained layer 66 in order to electric current perpendicular to efficient the scattering on the plane of its injection direction, its composition of composition (between 0.1 to 0.5) of aluminium is also littler than p type upper layer packets coating 64 in the strained layer 66 in the middle of thin, and will with the lattice match of p type upper layer packets coating 64.Thickness about 50 to l00nm, is low resistance channels that design produces the injection current vertical plane and ooze the assorted density intermediate current dispersion layer 68 higher than p-type conductance layer greatly.In addition, thin in the middle of strained layer 66 energy gap bigger than active area arranged, be adsorbed by the light of active area emission preventing.
But since this one thin in the middle of strained layer 66 very thin thickness and have one than p-type upper layer packets coating 64 high than window layers 70 low ooze assorted concentration, can be used as electric current on the barrier layer of growth direction and the low impedance channel of electric current incident growth direction vertical plane.Therefore according to above-mentioned, the lifting of the light emission efficiency of light-emitting diode 50 will be by In in p type upper layer packets coating 64 and the electric current dispersion effect in the active area
0.5(Ga
1-xAl
x)
0.5The thickness on P barrier layer, composition and doping level and decide.
Then, be one of the important feature of the present invention, a kind of meeting makes In
0.5(Ga
1-xAl
x)
0.5The approach that P light-emitting diode 50 produces the maximum function performance is at p type In
0.5(Ga
1-xAl
x)
0.5Add layer window layer 70 on the P layer.Use GaP, AlGaP or AlGaAs window layers 70, because the light that GaP or GaAsP radiate out for the active area by light-emitting diode 50 has a relative light-permeable energy gap.Utilizing the organic metal vapour phase epitaxy method to grow up among the present invention in direction＜111 of cutting sth. askew〉light emitting diode construction 50 comprises p type GaP, AlGaP or AlGaAs window layers 70 in the GaAs substrate 52 of angle.Epitaxial deposition AlGaAs, GaP or other family's semiconductor surface with liquid phase vapour phase epitaxy method or chemical vapour deposition (CVD) epitaxial growth mode to improve the flatness of deposit film.And in the present invention, three-five compounds of group such as GaP, Al
xGa
1-xP, wherein x is less than 0.1 and Al
yGa
1-yAs, wherein y is less than 1 greater than 0.5, GaP and Al
xGa
1-xP works as in 650 to 565nm scopes at light-emitting diode radiation wavelength to disperse injection current as window layers 70, because GaP, Al
xGa
1-xP is transparent for radiation wavelength 650 to 565nm.
In addition, luminous efficiency also has relation with the thickness of window layers 70.When window layers thickness increases because than scatter area and all can be increased by the light that led sides sheds of the electric current of width, the output of light-emitting diode also can increase.
Therefore, we can obtain, and utilize thinner thickness and angle of inclination towards＜111〉the A face with and mis-cut angle greater than the GaAs substrates of 10 degree as the substrate of light-emitting diode, can save the technology cost; Temperature when temperature gradient (thermal gradient) minimum when in addition, its substrate forms can be controlled at epitaxial growth at an easy rate; Moreover the also more traditional GaAs substrate of its luminous efficiency and heat radiation degree comes well.
The above is preferred embodiment of the present invention only, is not in order to limit protection scope of the present invention; All other do not break away from the equivalence of being finished under the disclosed spirit and changes or modification, all should be included in the scope of claims.
Claims (9)
1. a light emitting diode construction is characterized in that, this light emitting diode construction comprises:
One underlying metal contact layer;
One has a GaAs substrate of one first conductivity, and this GaAs substrate is positioned at this above underlying metal contact layer, and this GaAs substrate angle of inclination greater than 10 the degree, and cut sth. askew towards＜111 the A face;
One has a resilient coating of first conductivity, and this resilient coating is positioned at this above GaAs substrate;
One has a reflection layer of this first conductivity, this reflection layer be positioned at this resilient coating above;
One has one first coating layer of this first conductivity, and this first coating layer is positioned at this above light antireflecting layer;
One active layer, this active layer are positioned at this above first coating layer;
One has one second coating layer of one second conductivity, and this second coating layer is positioned at this above active layer, and wherein this second conductivity is in contrast to this first conductivity;
One intermediate barrier layers, this intermediate barrier layers are positioned at this above second coating layer;
One current barrier layer, this current barrier layer is positioned at this above intermediate barrier layers;
One window layers, this window layers is positioned at this above current barrier layer; And
One top-level metallic contact layer, this top-level metallic contact layer is positioned at this above window layers.
2. light emitting diode construction as claimed in claim 1 is characterized in that, above-mentioned GaAs substrate angle of inclination is 15 degree.
3. light emitting diode construction as claimed in claim 1 is characterized in that, the thickness range of above-mentioned GaAs substrate is 150 to 250 microns.
4. light emitting diode construction as claimed in claim 1 is characterized in that, the thickness of above-mentioned GaAs substrate is 210 microns.
5. light emitting diode construction as claimed in claim 1 is characterized in that, above-mentioned active layer comprises a strain and unadulterated In
y(Ga
1-xAl
x)
1-yP/In
0.5(Ga
1-xAl
x)
0.5P-structure.
6. a light emitting diode construction is characterized in that, this light emitting diode construction comprises:
One underlying metal contact layer;
One to have one first conductivity and thickness range be a GaAs substrate of 150 to 250 microns, and this GaAs substrate is positioned at this above underlying metal contact layer, and wherein this GaAs substrate angle of inclination is greater than 10 degree, and cuts sth. askew towards＜111〉the A face;
One has a resilient coating of one first conductivity, and this resilient coating is positioned at above the GaAs substrate;
One has a Bragg reflecting layer of this first conductivity, and this Bragg reflecting layer is positioned at this above resilient coating;
One has one first coating layer of this first conductivity, and this first coating layer is positioned at this above Bragg reflecting layer;
One active layer, this active layer are positioned at this above first coating layer;
One has In
y(Ga
1-xAl
x)
1-yP/In
0.5(Ga
1-xAl
x)
0.5One electron reflection layer of P superlattice structure, this electron reflection layer is positioned at this above active layer;
One has one second coating layer of one second conductivity, and this second coating layer is positioned at this above electron reflection layer, and wherein the thickness of this second coating layer is thicker than this first coating layer, and this second conductivity is in contrast to this first conductivity;
One intermediate barrier layers, this intermediate barrier layers are positioned at this above second coating layer;
One current barrier layer, this current barrier layer be positioned at this intermediate barrier layers above;
One window layers, this window layers be positioned at current barrier layer above, wherein this window layers is as the electric current that disperses to be positioned at this light emitting diode construction; And
One top-level metallic contact layer, this metal contact layer be positioned at this window layers above.
7. light emitting diode construction as claimed in claim 6 is characterized in that, above-mentioned GaAs substrate angle of inclination is 15 degree.
8. light emitting diode construction as claimed in claim 6 is characterized in that, the thickness of above-mentioned GaAs substrate is 210 microns.
9. light emitting diode construction as claimed in claim 6 is characterized in that, above-mentioned active layer comprises a strain and unadulterated In
y(Ga
1-xAl
x)
1-yP/In
0.5(Ga
1-xAl
x)
0.5The P multiple quantum trap.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB021285136A CN1230923C (en) | 2002-08-09 | 2002-08-09 | Light-emitting diode structure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB021285136A CN1230923C (en) | 2002-08-09 | 2002-08-09 | Light-emitting diode structure |
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|---|---|
| CN1474463A CN1474463A (en) | 2004-02-11 |
| CN1230923C true CN1230923C (en) | 2005-12-07 |
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| CN101527341B (en) * | 2008-03-07 | 2013-04-24 | 展晶科技(深圳)有限公司 | III-family nitrogen compound semiconductor light-emitting diode |
| DE102010014177A1 (en) * | 2010-04-01 | 2011-10-06 | Jenoptik Polymer Systems Gmbh | Surface emitting semiconductor light emitting diode |
| TWI572060B (en) * | 2015-11-20 | 2017-02-21 | 國立中興大學 | Light-emitting diode and manufacturing method thereof |
| CN107919417A (en) * | 2016-10-09 | 2018-04-17 | 比亚迪股份有限公司 | Light emitting diode and preparation method thereof |
| TWI742714B (en) * | 2019-06-11 | 2021-10-11 | 全新光電科技股份有限公司 | Semiconductor laser diode |
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Assignee: Luxtaltek Corporation Assignor: Zhoulei Science &. Technology Co., Ltd. Contract record no.: 2010990001031 Denomination of invention: Light-emitting diode structure Granted publication date: 20051207 License type: Exclusive License Open date: 20040211 Record date: 20101231 |
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