CN205452332U

CN205452332U - GaP roughened surface's alGaInP base LED

Info

Publication number: CN205452332U
Application number: CN201521068093.8U
Authority: CN
Inventors: 徐洲; 杨凯; 何胜; 李波; 李俊承; 林鸭亮; 赵宇; 徐培强; 张永; 张双翔
Original assignee: Yangzhou Changelight Co Ltd
Current assignee: Yangzhou Changelight Co Ltd
Priority date: 2015-12-21
Filing date: 2015-12-21
Publication date: 2016-08-10
Anticipated expiration: 2025-12-21

Abstract

GaP roughened surface's alGaInP base LED belongs to the semiconductor technology field, follows supreme back electrode, gaAs substrate, gaAs buffer layer, DBR speculum layer, n type limiting layer, MQW multi -quantum well active layer, p type limiting layer, p type gaP window layer and ITO electric current extension layer and the central electrode of being in proper order down, its characterized in that p type gaP window layer is the alligatoring form on one side of ITO electric current extension layer, set up the ohmic contact point between p type gaP window layer and ITO electric current extension layer. The utility model discloses can further improve alGaInP base LED's luminous efficiency to improve electric light conversion efficiency, the absorptive light of LED material itself reduces, and calorific capacity is corresponding reducing also, thereby can prolong LED's life -span.

Description

The AlGaInP base LED of GaP surface coarsening

Technical field

This utility model belongs to technical field of semiconductors, is specifically related to structure and the manufacture method thereof of AlGaInP base LED.

Background technology

The AlGaInP sill mated with GaAs substrate lattice is a kind of direct band-gap semicondictor, and by adjusting the ratio of Al and Ga, energy gap can change between 1.9eV～2.3eV, and the wave-length coverage of AlGaInP base LED can cover 550nm～650nm.Therefore, AlGaInP sill is widely used to HONGGUANG, orange light, the manufacture of green-yellow light LED.Owing to refractive index n of AlGaInP sill is up to 3.0～3.5, far above LED conventional encapsulation materials such as epoxy resin, silica gel (n ≈ 1.5).Total reflection law according to light, light enters optically thinner medium from optically denser medium can produce total reflection phenomenon in interface, and the refractive index difference of both sides, interface is the biggest, and the cirtical angle of total reflection is the least.This makes the light extraction efficiency of AlGaInP base LED the lowest.It is true that this problem exists in GaAsLED and GaNLED.

To this, I.Schnitzer etc. proposes the method [Appl.Phys.Lett., Vol.63, No.16,2174-2176, (1993)] that surface coarsening improves the external quantum efficiency of GaAsLED.S.Fan etc. propose the optical coupling output using 2 D photon crystal to be sent by active area, thus improve light extraction efficiency [Phys.Rev.Lett., Vol.78, No.17,3294-3297, (1997)].AlGaInPLED chip cutting is become rescinded angle reverse pyramid (truncated-inverted-pyramid) by M.R.Krames etc., thus change the angle between the light of directive sidewall and sidewall normal direction, reduce interface total reflection, improve light extraction efficiency [Appl.Phys.Lett., Vol.75, No.16,2365-2367, (1999)].C.S.Chang etc. use optical graving for mask pattern, then use ICP to be dry-etched in GaNLED sidewall to form semicircle periodic patterns, improve light extraction efficiency [IEEEPhotonic.Technol.Lett., Vol.16, No.3,750-752, (2004)].

In the above-mentioned methods, the method being improved LED light extraction efficiency by surface coarsening is widely used by industry, becomes a kind of conventional techniques of LED industry.Hao Xiaopeng et al. proposes employing ITO particle mask, the method [Chinese utility model patent, Authorization Notice No. CN101656284] of dry etching roughening GaP.Liao Wei et al. proposes employing dry etching and wet etching combines the method [Chinese utility model patent, application number 201410239956.7] making the GaP on LED chip surface be roughened.Yang Haifang et al. proposes employing dry etching and forms class spherical structure or the method [Chinese utility model patent, application number 201310061485.0 and 201310093588.5] of cone structure on GaP surface.But, above-mentioned art solutions pertains only to GaP surface coarsening, is not directed to GaP surface and covers ITO current extending.Xiao Zhiguo et al. proposes photoetching and wet etching combines and forms periodic texture the method carrying out surface coarsening on GaP surface, and propose to cover the ITO scheme [Chinese utility model patent, application number 201110363791.0] as current extending on GaP surface.But, this patent is not directed to the problem how GaP Yu ITO of surface coarsening forms Ohmic contact.After GaP surface coarsening, its surface height is mixed layer and is destroyed, and ITO is difficult to be formed Ohmic contact with the GaP layer of surface coarsening, thus causes LED chip forward voltage abnormal high.

Utility model content

GaP Yu ITO for surface coarsening mentioned above is difficult to be formed the problem of Ohmic contact, the utility model proposes the AlGaInP base LED of a kind of GaP surface coarsening.

This utility model sequentially consists of back electrode, GaAs substrate, GaAs cushion, DBR mirror layer, N-shaped limiting layer, MQW multiple quantum well active layer, p-type limiting layer, p-type GaP Window layer and ITO current extending and main electrode；It is characterized in that p-type GaP Window layer towards ITO current extending side in roughening shape, Ohmic contact point is set between p-type GaP Window layer and ITO current extending.

This utility model beneficial effect: (1) can improve the light extraction efficiency of AlGaInP base LED further, thus improves electro-optical efficiency；(2) improving due to light extraction efficiency, the light that LED material itself absorbs reduces, and caloric value reduces the most accordingly, such that it is able to extend the life-span of LED.

Further, the pattern of roughening shape described in the utility model is acyclic random figure, and described dimension of picture is submicron order.Acyclic random figure, can have scattering and diffracting effect to the light of different wave length, if periodically regular figure, then the most effective to the light of specific wavelength.Owing to LED described in present patent application is visible LED, the figure of submicron order more efficiently can produce scattering and diffraction to the light of this wave band.

Described dimension of picture is 50nm～1 μm.This dimension of picture is on the one hand in order to obtain higher light extraction efficiency, and roughening dimension of picture should be comparable with visible wavelength range 380nm to 760nm；On the other hand, the fluctuating degree of depth of roughening figure can not be too big, and the phenomenon in order to avoid the ITO current extending that surface covers does not plans a successor causes electric current effectively not extend.

Accompanying drawing explanation

Fig. 1 is a kind of cross-sectional view of the present utility model.

Fig. 2 is the top view of Fig. 1.

Wherein, 101 is back electrode, i.e. n-electrode, 102 be GaAs substrate, 103 be GaAs cushion, 104 be DBR mirror layer, 105 be N-shaped limiting layer, 106 be MQW multiple quantum well active layer, 107 be p-type limiting layer, 108 be p-type GaP Window layer, 109 be Ohmic contact point, 110 be ITO current extending, 111 for main electrode, i.e. p-electrode.

Detailed description of the invention

One, combine Fig. 1,2 describe in detail manufacturing technology steps of the present utility model:

1, use MOCVD device at GaAs substrate 102 growing epitaxial layers, form AlGaInP base LED epitaxial wafer.Epitaxial layer includes GaAs cushion 103, DBR mirror layer 104, N-shaped limiting layer 105, MQW multiple quantum well active layer 106, p-type limiting layer 107, p-GaP Window layer 108.

Wherein the preferred thickness of p-GaP Window layer 108 is 600nm to 8000nm, and doping content is 1 × 10¹⁸cm^-3Above, doped chemical is Mg, to ensure to form good electrical contact with Ohmic contact point 109, and has good current expansion ability.

2, acetone, isopropanol, deionized water is used to clean the p-GaP Window layer 108 in epitaxial wafer front successively, nitrogen dries up, by spin coating negative photoresist, mask pattern is made in exposure, development, Au, Lift-off technique at AuZn and 200nm that p-GaP Window layer 108 surface evaporation thickness is 300nm completes the making of Ohmic contact point 109.AuZn Yu p-GaP Window layer forms good electrical contact through nitrogen atmosphere 440 DEG C annealing 10min.

The material of Ohmic contact point can also use in Au, Pt, Ti, Cr, Al, Ni, AuBe, AuZn, AuGe or AuGeNi at least any one.

3, p-type GaP Window layer 108 surface is prepared in the epitaxial wafer immersion coarsening solution of Ohmic contact point 109 and carry out being roughened without mask.Rinsing well with deionized water and isopropanol respectively after being roughened, nitrogen dries up.

In this example, coarsening solution uses volume ratio to be the H of 1:1:5₂SO₄:HF:CH₃COOH mixed liquor forms.

Coarsening solution can also use HCl, H₂SO₄、H₃PO₄、HNO₃、HBr、I₂Aqueous solution, CH₃COOH、HF、NH₄F、NH₄OH, KOH aqueous solution or H₂O₂In at least any one.

4, p-type GaP Window layer 108 and Ohmic contact point 109 surface in roughening use electron-beam vapor deposition method or magnetron sputtering embrane method one layer of ito film of deposition as current extending 110, and the thickness of ITO current extending 110 is 50nm～500nm, and this example selects 300nm.

5, at ITO current extending 110 surface spin coating negative photoresist, expose, develop formation main electrode graph window.

6, the Au of Pt and 2500nm of electron beam evaporation or Cr, 200nm that thermal evaporation thickness is 100nm is as main electrode.

7, Lift-off technique completes the making of main electrode 111, uses acetone, isopropanol, deionized water to clean the most successively, and nitrogen dries up.

8, the GaAs substrate 102 utilizing the crude product that step 7 makes by mechanical lapping mode is thinned to remain 150 μm.

9, at the Au of thinning AuGe and 200nm that GaAs substrate 102 back side evaporation thickness is 100nm as back electrode 101.

10, carry out, at 450 DEG C of nitrogen atmosphere annealing furnaces, 5min process of annealing, make to be formed between back electrode 101 and GaAs substrate 102 good electrical contact, and strengthen the adhesive force between back electrode 101 and GaAs substrate 102；Also make all to be formed between main electrode 111 and ITO current extending 110 and between ITO current extending 110 and Ohmic contact point 109 good electrical contact simultaneously, and strengthen the adhesive force between main electrode 111 and ITO current extending 110.

11, crude product front hemisection step 10 made, half cutting depth 20um to 100um.Then testing photoelectronic parameter, finally cut through, complete LED chip manufacturing process.

Two, the product structure feature made:

As it is shown in figure 1, sequentially consist of back electrode 101, GaAs substrate 102, GaAs cushion 103, DBR mirror layer 104, N-shaped limiting layer 105, MQW multiple quantum well active layer 106, p-type limiting layer 107, p-type GaP Window layer 108 and ITO current extending 110 and main electrode 111；It is provided with Ohmic contact point 109 between p-type GaP Window layer 108 and ITO current extending 110.P-type GaP Window layer 108 towards ITO current extending 110 side in roughening shape.

As in figure 2 it is shown, the size of Ohmic contact point 109, shape and distribution can be adjusted according to the operating current of chip size and LED chip.

Claims

The AlGaInP base LED of 1.GaP surface coarsening, sequentially consists of back electrode, GaAs substrate, GaAs cushion, DBR mirror layer, N-shaped limiting layer, MQW multiple quantum well active layer, p-type limiting layer, p-type GaP Window layer and ITO current extending and main electrode；It is characterized in that p-type GaP Window layer towards ITO current extending side in roughening shape, Ohmic contact point is set between p-type GaP Window layer and ITO current extending.