CN202957285U

CN202957285U - Epitaxial structure of improving LED lateral luminous efficiency effectively

Info

Publication number: CN202957285U
Application number: CN201220470721.5U
Authority: CN
Inventors: 陈立人; 陈伟; 刘慰华
Original assignee: FOCUS LIGHTINGS TECH Inc
Current assignee: Focus Lightings Technology Suqian Co ltd
Priority date: 2012-09-17
Filing date: 2012-09-17
Publication date: 2013-05-29
Anticipated expiration: 2022-09-17

Abstract

The utility model discloses an epitaxial structure of improving an LED lateral luminous efficiency effectively and a method for manufacturing the same. In the utility model, a GaN/A1GaN superlattice structure is employed to substitute a general GaN epitaxial layer, and the epitaxial layer of a semiconductor epitaxial device is equipped with a sapphire substrate, a buffer layer, an N-type layer, a luminescent layer, the GaN/A1GaN superlattice and a P-type layer orderly from bottom to top, wherein the GaN/A1GaN superlattice is next to the last quantum barrier of a multiple quantum well. An LED device of the utility model is based on a principle that the etching speeds of the GaN and the A1GaN are different by employing an ICP etching method, so that the lateral zigzag contour of an LED chip is realized. The epitaxial structure of improving the LED lateral luminous efficiency effectively enables the luminous area of a side wall of the chip to be increased and the luminous angle of the chip to be changed, so that the luminous efficiency of photons from the side surface of a GaN/A1GaN superlattice layer can be improved effectively. The epitaxial structure of improving the LED lateral luminous efficiency effectively of the utility model enables the luminous efficiency of the chip to be improved by more than10% via a sidewall microstructure process technology.

Description

A kind of epitaxial structure of effective raising LED side bright dipping

Technical field

The utility model relates to the compound semiconductor device field, especially relates to a kind of LED chip structure that can effectively improve the side bright dipping.

Background technology

The solid-state illumination light source of light-emitting diode (LED) is because it is low in energy consumption, the life-span is long, volume is little and the pursuing of the high people of being subject to of reliability.And so, it is exactly that its luminous efficiency is lower that GaN base LED has a very large defect.The internal quantum efficiency of GaN base LED has reached 90%, and the external quantum efficiency of common LED is because the impact that is subject to total reflection is only 5%.The product that external quantum efficiency is internal quantum efficiency and extraction efficiency, luminous efficiency is limited by external quantum efficiency mainly.The photon sent from the LED active layer, needing to see through device inside could arrive in air.The GaN material be refracted as 2.4, the refractive index of air is 1. 0, the angle of total reflection 24. 5, the photon that is greater than the angle of total reflection will be reflected back (Hao M, Egawa T, Ishikawa H. Highly efficient GaNbased light emitting diodes with micro pits [J]. Appl. Phys. Lett., 2006,89:241907).

For traditional rectangular cavity configuration LED, its structure as shown in Figure 1, this structure comprises growth substrates 1, N-type GaN layer 2, MQW active layer 3, p-AlGaN layer 5 and p-type GaN layer 6, the photon that is greater than the angle of total reflection can be at device inside Multi reflection back and forth, in the Multi reflection process, some photon can arrive the side of device, by the side outgoing, part photon all the time can't outgoing and finally be absorbed in the Multi reflection process, approximately only has in theory 20% photon energy from device outgoing (Windisch R, Dutta B, Kuijk M, et al. 40% efficient thin film surface textured light emitting diodes by optimization of natural lithography [J]. Electron Devices, 2000, 47:1492-1498).In order to make more photon escape out, can carry out alligatoring (Fujii T to device surface, Gao Y, Nakamur a S, et al. Increase in the extraction efficiency of GaN based light emitting diodes via surface roughening [J]. Appl. Phy s. Lett., 2004,84 (6): 855-857).For traditional LED devices such as GaA s base, by natural lithography and ICP lithographic method (Deng Biao, Liu Baolin. the side alligatoring improves GaN base LED light extraction efficiency research [J]. semiconductor optoelectronic, 2011,32(3): 352-354), effects on surface carries out alligatoring effectively.Yet, for GaN base LED, because the p-type layer is very thin, and etching depth is wayward, after etching, device is caused to very large damage, realize commercial applications very difficult (Li Fen. GaN base LED surface coarsening structure Study on Preparation Technology [D]; Xian Electronics Science and Technology University; 2011).Therefore, alligatoring is carried out in the side of device and reach that to improve that light extraction efficiency do not stint be a method preferably.

Do not considering in the absorbed situation of light, the photon that active area produces is during to the device surface bright dipping, when incidence angle is greater than the angle of total reflection (approximately 24.5 °), photon is because total reflection will carry out back reflective at device inside, and by the repeatedly extinction of GaN material, finally decay to zero, a part of photon can't see through device surface all the time.Wherein a part of photon can finally will be gone out from the side of chip through Multi reflection by chip surface and inside.Arrive the photon of device side for these; side now is equivalent to the surface of device; there is equally the total reflection problem; so; alligatoring is carried out in side and can reach the effect identical with surface coarsening, thus the light extraction efficiency of raising LED (Wei Wei. the laterally inclined research [D] that improves GaN base LED light extraction efficiency in roughening; Changchun University of Science and Technology; 2007).In traditional GaN base LED preparation process, when carrying out mesa etch, utilize the principle that the ICP etching is different from the AlGaN etching speed to GaN, realize jagged side, LED chip side after etching, this method is very easy on technique realizes, need not increase any chip technology flow process, practical value is very high.

Summary of the invention

The purpose of this utility model is for the low problem of LED chip side light emission rate of the prior art, and a kind of LED chip structure that increases the side light emission rate is provided.

For achieving the above object, the technical solution of the utility model is: a kind of epitaxial structure of effective raising LED side bright dipping, this structure is positioned on growth substrates, comprise N-type layer, active layer, GaN/AlGaN superlattice layer, and the p-type layer, wherein, the lateral edge of described GaN/AlGaN superlattice layer cross section has zigzag or corrugated profile, by sidewall micro-structural technology, can improve the light extraction efficiency of chip more than 10%.

As further prioritization scheme, described growth substrates comprises Si substrate, SiC substrate, plane or graphical sapphire substrate.

As further prioritization scheme, the gross thickness of described GaN/AlGaN superlattice layer is less than or equal to 30 nm.

Compared with prior art, the utility model adds by superlattice structure, utilizes the ICP etching inconsistent to the etching speed of bi-material, realizes the purpose of chip sides alligatoring, thereby improve the side light extraction efficiency of LED chip, can effectively promote the external quantum efficiency of chip; Owing to only having introduced superlattice layer, thereby without increasing in addition any chip technology, fully compatible with existing chip technology.

The accompanying drawing explanation

Accompanying drawing 1 is the cross-sectional view of traditional LED epitaxial wafer;

Accompanying drawing 2 is cross-sectional view of the LED epitaxial wafer with GaN/AlGaN superlattice of the embodiment of the present invention;

Accompanying drawing 3 is cross-sectional view of the positive cartridge chip of LED with GaN/AlGaN superlattice of the embodiment of the present invention.

Embodiment

Below in conjunction with accompanying drawing, preferred embodiment of the present utility model is described in detail, thereby so that advantage of the present utility model and feature can be easier to be it will be appreciated by those skilled in the art that, protection range of the present utility model is made to more explicit defining.

Shown in accompanying drawing 2 and accompanying drawing 3, a kind of epitaxial structure of effective raising LED side bright dipping, this structure is positioned on growth substrates 1, comprise N-type GaN layer 2, MQW active layer 3, GaN/AlGaN superlattice layer 4, p-AlGaN layer 5 and p-type GaN layer 6, wherein, GaN/AlGaN superlattice layer 4 is close to last quantum of Multiple Quantum Well (MQW) and builds, this superlattice layer need to be at same air pressure, same temperature, the film of growing under same atmosphere, the lateral edge of its cross section has zigzag or corrugated profile as shown in Figure 3, the gross thickness of GaN/AlGaN superlattice layer 4 is less than or equal to 30 nm.

In addition, it is to be noted that growth substrates 1 comprises Si substrate, SiC substrate, plane or graphical sapphire substrate, and the below of N-type layer can also be provided with a resilient coating.

The manufacturing process of this epitaxial structure below is described in detail in detail.

At first, in brilliant process of heap of stone, generate successively N-type GaN layer 2 on growth substrates 1, MQW active layer 3, GaN/AlGaN superlattice layer 4, p-AlGaN layer 5 and p-type GaN layer 6, GaN/AlGaN superlattice layer 4 is in same pressure, temperature, under atmosphere, growth generates, insert a GaN/AlGaN superlattice layer 4 between MQW active layer 3 and p-type GaN layer 6, GaN/AlGaN superlattice layer 4 is close to last quantum of Multiple Quantum Well (MQW) and builds, GaN/AlGaN superlattice layer 4 gross thickness are no more than 30 nm, GaN is the layer that undopes, AlGaN layer Al component approximately 15%, to reach ICP to the inconsistent requirement of two-layer etching speed, wherein need to mix a small amount of In in the AlGaN layer, adjust crystal lattice stress, In component 5%-8%.

Secondly, in the ICP etching process, adjust ICP etching power and etching speed and reach the purpose of side alligatoring with the speed of distinguishing AlGaN and GaN layer, by the pulse frequency of regulating lasing light emitter, the lateral edge of described GaN/AlGaN superlattice layer is divided into to zigzag or corrugated profile, this micro-structural has increased the lighting area of chip sidewall, change the rising angle of chip, thereby can effectively improve the efficiency of photon from the 4 side bright dippings of GaN/AlGaN superlattice layer.

Finally, prepare electrode and follow-up all the other techniques on semiconductor epitaxial layers.

Above execution mode is only explanation technical conceive of the present utility model and characteristics; its purpose is to allow the person skilled in the art understand content of the present utility model and implemented; can not limit protection range of the present utility model with this, all equivalences of doing according to the utility model Spirit Essence change or modification all is encompassed in protection range of the present utility model.

Claims

1. an epitaxial structure that effectively improves the bright dipping of LED side, it is characterized in that: this structure is positioned on growth substrates, comprise N-type layer, active layer, GaN/AlGaN superlattice layer, and p-type layer, wherein, the lateral edge of described GaN/AlGaN superlattice layer cross section has zigzag or corrugated profile.

2. the epitaxial structure of a kind of effective raising LED side bright dipping according to claim 1, it is characterized in that: described growth substrates comprises Si substrate, SiC substrate, plane or graphical sapphire substrate.

3. the epitaxial structure of a kind of effective raising LED side bright dipping according to claim 1, it is characterized in that: the gross thickness of described GaN/AlGaN superlattice layer is less than or equal to 30 nm.