CN1149684C

CN1149684C - High-brightness LED

Info

Publication number: CN1149684C
Application number: CNB981193498A
Authority: CN
Inventors: 张盼梓; 陈泽澎; 杜全成
Original assignee: GUOLIAN PHOTOELECTRIC SCIENCE AND TECHNOLOGY Co Ltd
Current assignee: Epistar Corp
Priority date: 1998-09-21
Filing date: 1998-09-21
Publication date: 2004-05-12
Anticipated expiration: 2018-09-21
Also published as: CN1248799A

Abstract

The present invention relates to a high-brightness LED which comprises a semiconductor chip with conductivity, a lower limiting layer with first conductivity, an aluminium gallium indium phosphide work layer with no doped impurity or a multiple quantum-well structure, and an upper limiting layer structure with second conductivity. The upper limitating layer structure comprises four-element semiconductor material-the aluminum phosphide gallium indium (Al<x>Ga<1-x>) In<1-y>P, a layer of thin material with high resistance is added in the structure to improve the brightness of the LED.

Description

High brightness LED

Technical field

The present invention relates to a kind of light-emitting diode, be meant the high brightness LED that a kind of AlGaInP is formed especially.

Background technology

AlGaInP (Al _xGa _1-x) _yIn _1-yThe plain compound of P quaternary is the direct band gap semiconductor that a lattice constant and a GaAs (GaAs) substrate are complementary.The luminous efficiency of this compound between wavelength 560nm to 650nm is very high, therefore is fit to very much be used for making the light-emitting diode of emission wavelength from the redness to the yellow-green light.

Fig. 1 represents the generalized section of an AlGaInP light-emitting diode of using always, this diode has a n p type gallium arensidep substrate 100, one n type AlGaInP lower limit layer 101, undope the AlGaInP working lining 102 of matter and the AlGaInP upper limiting layer 103 of a P type.Be difficult to improve because the AlGaInP of P type mixes impurity concentration, the resistance of this upper limiting layer also thereby very high makes can't diffuse to the crystal grain edge at the electric current that is injected by the top metallic conduction utmost point.So working lining sent below top electrode has widely all been sponged by opaque electrode, the luminous intensity of this light-emitting diode also so not high.

In order to promote the diffusion of electric current, the U.S. the 5th, 008, No. 718 patents have adopted a kind of gallium phosphide transparency window floor of high band gap, utilize the low resistance of this window layer that electric current can be scattered into working lining equably.Though this window layer contains the P type gallium phosphide material of high impurity, because the mobility in electric hole is low, so resistance value is approximately only inferior than the little one-level of upper limiting layer, so the thickness of this window layer must be quite thick, just is enough to improve the wandering of electric current.

The transparency window layer of high thickness not only is difficult for growing up, and cost is also high, in order to lower the thickness of window layer, the U.S. the 5th, 359, No. 209 patent disclosures contain the window structure of two layers of material, wherein comprise a low band-gap and contain the p type gaas layer of high impurity and the gallium phosphide layer of a high band gap.The P p type gallium arensidep of high impurity has low-down resistance value, and its resistance is approximately inferior less than secondary than upper limiting layer.

Contain the window structure of two layers of material,,, make the thickness of whole window layer also must reduce so the resistance value of whole window structure also greatly reduces because the low resistance of the p type gaas layer of high impurity is arranged.But, also make this lumination of light emitting diode intensity reduce several percentage points because of opaque gallium arsenide layer because added the p type gaas layer of high impurity.

Summary of the invention

The time that the object of the present invention is to provide a kind of light-emitting diode of high brightness and reduce the growth diode is improved the shortcoming of above-mentioned diode commonly used.In order to reach this purpose, the present invention has added the very thin resistive formation of one deck in upper limiting layer.

High brightness LED of the present invention comprises: the GaAs substrate of a N type, the AlGaInP lower limit layer of a band N type, an AlGaInP working lining or a multiple quantum trap structure that undopes matter, and the upper limiting layer structure of the AlGaInP of band P type.AlGaInP (the Al of described band P type _xGa _1-x) _YIn _1-yP upper limiting layer structure comprises three layers, adjacent with the working lining AlGaInP layer AlGaInP (Al for can lattice being complementary with GaAs substrate and working lining in it _xGa _1-x) _yh _1-yP, wherein y=0.51.

The middle level of the upper limiting layer structure of described P type is very thin but AlGaInP semiconducting compound layer that resistance is very high, and its composition can be (Al _xGa _1-x) _yh _1-YAluminium composition X is bordering on 1 in the semiconducting compound of P, and indium composition 1-y is bordering on 0, and its impurity content is very little or undope matter.For ease of making top electrode, the upper strata of this upper limiting layer structure is high band gap and high conductive layer, and its composition can be (Al _xGa _1-x) _YIn _1-YP, wherein aluminium composition X is bordering on 0, and indium composition 1-y also is bordering on 0, the content of indium＜30%.Because a middle level resistive formation has been arranged, the electric current that injects is forced to be evenly distributed on the upper strata of upper limiting layer structure, and then enter working lining by intermediate layer and lower floor, so whole working lining can uniformly light-emitting and the luminous intensity of high brightness LED of the present invention is strengthened.

Description of drawings

Fig. 1 is the generalized section of AlGaInP light-emitting diode commonly used;

Fig. 2 is the generalized section of first kind of structure of AlGaInP high brightness LED of the present invention;

Fig. 3 is the generalized section of second kind of structure of AlGaInP high brightness LED of the present invention.

Embodiment

With reference to Fig. 2 and Fig. 3, high brightness LED of the present invention comprises the GaAs substrate 200 of a N type, the AlGaInP lower limit layer 201 of the band N type of on this substrate, growing up, on lower limit layer is the multiple quantum trap structure 302 of an AlGaInP working lining 202 or AlGaInP, quantum well structure 302 is to be formed by quantum well layer 3021 and the alternately folded group of barrier layer 3022, and its structure as shown in Figure 3.

Luminescent layer of the present invention that is working lining are by (Al _xGa _1-x) _yIn _1-yP, wherein X can be from 0 to 0.4, its value is decided by luminous wavelength.If X is 0.15 o'clock, it sends the about 610nm of light wavelength, limiting structure 203 on the AlGaInP that above this working lining is band P type.Upper limiting layer of the present invention is the structure with three-layer-material, and wherein the contacted one deck of orlop and luminescent layer is by (Al _xGa _1-x) _yIn _1-yThe AlGaInP layer 2031 that P forms, lattice constant of this layer and GaAs are complementary in order to avoid produce dislocation, and wherein the composition of aluminium from 0.7 to 1 is to reach electronics restriction effect preferably.The intermediate layer is a very thin resistive formation 2032, can utilize a lot of different modes to form this layer, such as phosphatization gallium aluminium or aluminum phosphate contains low concentration impurity, and the resistive formation 3032 of about 200 dusts of thickness all is suitable intermediate layer.

In general, increase at aluminium component can be along with increase, so (Al when reducing with impurity concentration for the resistance of AlGaInP semiconducting compound _xGa _1-x) _yIn _1-yAluminium component height in the material that P forms and indium composition impurity low and that contain low concentration promptly can be the good selection in this intermediate layer, and the composition of this resistive layer 2032 is 0.7≤X≤1.0 and 0.9≤y≤1.0 and the (Al that forms preferably _xGa _1-x) _yIn _1-yP.

This intermediate layer optimum thickness be 0.005 μ m to 0.1 μ m, composition wherein might not be fixed, and for example forms with the superlattice structure of AlGaInP such as AlP/GaP or the gradual change of AlGaP/GaP or AlGaInP, composition is by (Al _xGa _1-x) _0.51In _0.49The material that P is gradient to AlGaP or AlP can be used for as the resistive formation 2032 of thin intermediate.

The upper strata then is with (Al _xGa _1-x) _yIn _1-yThe conductive contact layer 2033 that the high band gap low resistance of P is a material, wherein, 0≤X≤0.1, and 0.7≤y≤1.The necessary condition of this conductive contact layer 2033 is must have than the higher band gap of working lining in order to avoid absorb light.In addition, the concentration of its impurity must height and resistance value must be hanged down in order to the formation with high conductivity AlGaInP semiconducting compound, be easier to add impurity to increase the carrier concentration of this layer if aluminium component is low, preferably composition is AlGaInP (Al _xGa _1-x) _yIn _1-yContain aluminium among the P less than 10%.Yet for avoiding absorbing light, the composition of indium must be less than 30%.

Because contain the intermediate layer of a resistive formation 2032 and the upper strata of low resistance conductive contact layer 2033 in this upper limiting layer structure, the electric current that injects from top contact electrode is forced to evenly scatter and passes through centre resistive formation 2032 and lower floor's AlGaInP layer 2031 then again to luminescent layer at last conductive contact layer 2033.After the resistive formation 2032, low-resistance upward conductive contact layer 2033 thickness of this high band gap are thinner than what use always, about 0.5 μ m to the 10 μ m of its thickness in the middle of having added this.Adding the shortcoming that this resistive formation 2032 caused is that forward bias slightly increases.

High brightness LED luminous intensity of the present invention just greatly increases, and below enumerates the embodiment of several actual experiments.

Embodiment 1

High brightness diode structure of the present invention such as Fig. 2, growth shown in Figure 3 are on a n p type gallium arensidep substrate 200, and its growth is with to 2 ° of [111] deviations of directivity, and impure concentration 1 * 10 ¹⁸Cm ^-3The about 350 μ m of the thickness of n p type gallium arensidep substrate 200, the impurity concentration 1 * 10 of growing up in the above earlier ¹⁸Cm ^-3N p type gallium arensidep resilient coating, again the AlGaInP lower limit layer 201 of 1 μ m gauge strips n type conductivity is grown up on resilient coating.

It above n type AlGaInP lower limit layer 201 luminescent layer with AlGaInP working lining 202 formation of the matter that undopes.The AlGaInP working lining 202 of this matter that undopes can be the multiple quantum trap structure 302 (as shown in Figure 3) of the matter that undopes, and its structure comprises multilayer AlGaInP (AlGa) InP quantum well layer 3021 and the alternately folded group of multilayer AlGaInP (AlGa) InP barrier layer 3022 forms.

The AlGaInP working lining 202 of the matter that undopes or the top of multiple quantum trap structure 302 are P type AlGaInP (AlGa) InP upper limiting layer structure 203, the P type AlGaInP or the InGaP (In that wherein comprise the high impurity of the phosphatization gallium aluminium of P

type AlGaInP layer

2031,200 dust of 1 μ m or AlGaInP resistive formation 2032 and 5 μ m _0.1Ga _0.9P) conductive contact layer 2033.

For the ease of relatively, also prepared a light-emitting diode commonly used in the experiment, the present invention and diode commonly used can both pass to the electric current of 20mA.Comparative result finds that the electric current of light-emitting diode of the present invention is wandering very good, and the auroral poles of dispersing from crystal grain is for evenly.Led lighting intensity of the present invention is about 65mcd between 590nm to 615nm, and the diode of traditional type then has only 40mcd, and the forward bias of diode of the present invention is approximately 2.2 volts, than high about 0.2 volt that uses always.

High brightness LED of the present invention, if adding in GaAs substrate and working lining that the distributing Bragg reflector reflects originally will be by the light of substrate absorption, luminous intensity then can increase again so, below is an experimental example.

Embodiment 2

Diode structure of the present invention is grown up on the GaAs substrate 300 of n type, and its growth direction is with 2 ° of [111] deviations of directivity, and contains impurity concentration 1 * 10 ¹⁸Cm ^-3The thickness of GaAs substrate is approximately 350 μ m, an earlier long thereon n p type gallium arensidep resilient coating, the concentration 1 * 10 of this resilient coating ¹⁸Cm ^-3

The one AlAs/GaAs distributing Bragg reflector that comprises 12 groups is grown up on the resilient coating of GaAs, n type (AlGa) the InP lower limit layer of about 1 μ m is grown up disperseing on the Bragg reflector again.Luminescent layer is made for the multiple quantum trap structure 302 of the AlGaInP of the matter that undopes in this n type lower limit layer top, and AlGaInP quantum well layer 3021 and the alternately folded group of AlGaInP barrier layer 3022 that described multi-layer quantum well structure 302 comprises multilayer form.

Above multiple quantum trap structure 302 the AlGaInP 3031 upper limiting layer structures of P type, this structure comprises the P type AlGaInP layer 3031 of 1 μ m, three groups of super crystal structures of GaP/AlP are used as resistive formation 3032, and the AlGaInP of the high impurity of one 5 μ m or InGaP (In _0.1Ga _0.9P) conductive contact layer 3033.Its thickness of super crystal structure with two kinds of different-thickness is respectively 45 dusts and 80 dusts.Two kinds of AlGaInP light-emitting diode luminances that produced all are 95mcd, are 2.15 volts and the forward voltage of the superlattice structure of 45 dust thickness is arranged, and are 3.3 volts and the forward voltage of the superlattice structure of 80 dust thickness is arranged.

Comprehensively described, high brightness LED of the present invention makes luminous intensity increase by 1.5 to 2 times because added a very thin resistive formation in the upper limiting layer structure, and unique deficiency is that forward bias has improved a little.Yet the present invention only needs the growth of a MOVPE, and the conductive contact layer thickness of top high band gap can reduce, so the advantage that the present invention has easy growth and reduces cost.

Claims

1, a kind of high brightness LED is characterized in that, comprises:

One N p type gallium arensidep substrate;

One is formed at the AlGaInP lower limit layer of N type on this substrate;

One is formed on this lower limit layer, the AlGaInP working lining of the matter that undopes; And

One upper limiting layer structure comprises:

Growth is the AlGaInP layer of the ground floor P type of lattice constant and described substrate coupling on described working lining;

Growth has the AlGaInP resistive layer of high-resistance second layer P type on the AlGaInP layer of described ground floor P type;

Growth is the high band gap high conductivity AlGaInP contact layer of the 3rd layer of P type, wherein: 0＜indium＜30% on the AlGaInP layer of above-mentioned second layer P type.

2, high brightness LED as claimed in claim 1 is characterized in that, the AlGaInP layer of the ground floor P type of described and substrate coupling, and aluminium component is 0.7～1 in its AlGaInP.

3, high brightness LED as claimed in claim 1 is characterized in that, the AlGaInP resistive layer of described second layer P type comprises (Al _sGal _1-s) _tLn _1-tP conductor material, and 0.7≤s≤1.0 and 0.9≤t≤1.0, thickness is 0.005～0.1 μ m.

4, high brightness LED as claimed in claim 3 is characterized in that, the AlGaInP resistive layer of described second layer P type, and it comprises superlattice structure such as AlP/GaP or the AlGaP/GaP of AlGaInP (AlGa) InP.

5, high brightness LED as claimed in claim 3 is characterized in that, the AlGaInP resistive layer of described second layer P type, and the gradual change that comprises AlGaInP (AlGa) InP is formed.

6, high brightness LED as claimed in claim 1 is characterized in that, the high band gap high conductivity AlGaInP contact layer of described the 3rd layer of P type comprises (Al _xGa _1-x) yln _1-yThe P semi-conducting material, wherein 0≤x≤0.1 and 0.7≤y≤1.0, thickness is 0.5～10 μ m.

As claim 1 or 6 described high brightness LEDs, it is characterized in that 7, the high band gap high conductivity AlGaInP contact layer of described the 3rd layer of P type contains in its AlGaInP: 0＜aluminium＜10%, 0＜indium＜30%.