RU2504867C2 - Method of making light-emitting diode - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: antireflection optical coating of SiO₂ is deposited on a light-emitting GaN-n or GaN-p surface and a microrelief is formed in said coating in form of nano-spikes with density of 10⁷-10⁸ items/cm². The present method enables to form a microrelief light-diffusing, light-emitting surface on both an n-type and p-type GaN without deterioration of heterostructure parameters.

EFFECT: high external quantum efficiency of GaN-based light-emitting diodes.

2 dwg, 1 ex

Description

A manufacturing method relates to the field of semiconductor light emitting devices and can be used for the production of LEDs.

A known method of manufacturing a semiconductor light emitting device [US 20040113163], comprising a substrate with a textured layer formed on its surface having a rough surface, as well as layers of nitride material grown by the epitaxy method, forming a semiconductor heterostructure with a p-n junction. Due to the presence of the indicated textured layer, the microprotrusions and microdroplets of which form light scattering centers, the effect on the light output of the effect of total internal reflection of light arising at the interface of the substrate — the material layer adjacent to the substrate — decreases when the refractive index of the material of the specified layer exceeds the refractive index substrate material. As a result, the proportion of light emitted through the substrate increases, and thereby the external optical efficiency of the device increases. The disadvantage of this method is that in relation to the main technological process of epitaxial growth of semiconductor layers, additional technological operations are required, including, for example, operations such as etching of the material of the layer, including the preliminary application of a photomask, the design and manufacturing technology of the device in question is complicated.

Also known is a method of creating LEDs based on GaN [EP 2218114] (the closest analogue), including texturing the light-conducting surface of the GaN-n type. Photolithography and plasmachemical etching of gallium nitride are used to form rough surfaces. Etching is carried out through windows with a diameter of 2 microns and a distance between centers of 8 microns. During etching, the side walls of the microprotrusion are tilted so that every time the beam is reflected, the angle of incidence of the beam on the side wall decreases. In this case, the angle of incidence of the rays is less than the critical angle, and the transmission of light through the side inclined surface increases.

The disadvantage of the proposed method is that the GaN substrate itself is etched, which negatively affects the parameters of heterojunctions and this method of creating rough surfaces is not suitable when light is output through a GaN-p type layer due to a very small pn junction (0.15-0.2 μm).

The aim of the invention is to increase the external quantum efficiency of a GaN-based LED.

This goal is achieved by depositing an antireflective optical coating 8O3 on the GaN surface and creating a microrelief in this coating. An increase in the external quantum efficiency is achieved due to the bleaching effect at the GaN-SiO ₂ interface and due to the presence of light-scattering microrelief in the SiO ₂ layer. A microrelief in the form of nano points with a density of 1.4 · 10 ⁷ pcs / cm ² is created using photolithography or electron beam lithography and subsequent etching of SiO ₂ .

In relation to the prototype, in the claimed invention, the microrelief is formed in an additional layer of SiO ₂ without the need for etching gallium nitride itself, which allows one to achieve the goal when outputting light both through GAN-n and through GAN-p type with a small heterojunction depth without compromising heterostructure parameters.

An example of a specific implementation of the method

A gallium nitride (GaN) -based heterostructure surface is coated with a silicon dioxide (SiO ₂ ) antireflection coating with an optical thickness corresponding to λ / 4 by magnetron sputtering with the removal of electron bombardment from the heterostructure. In the antireflection coating of silicon dioxide (SiO ₂ ), a microrelief surface of an ordered structure in the form of nano points is formed using electron beam lithography (Figure 1). The distance between the nano points 500 nm, the diameter of the base of the tip 284 nm, which corresponds to the density of the nano points 1.4 · 10 ⁷ pcs / cm ² (Figure 2).

INFORMATION SOURCES

1. Steigerwald, Daniel A. (Cupertino, CA, US) Bhat, Jerome C. (San Francisco, CA, US). Light emitting device with enhanced optical scattering. US20040113163; International Classes: G02B 5/02; H01L 33/22; G02B 5/02; H01L 33/00; (IPC1-7): H01L 33/00.

2. Zhong Hong [CN]; Tyagi Anurag [US]; Vampola Kenneth J [US]; Speck James S [US]; Denbaars Steven P [US]; Nakamura Shuji [US]. High light extraction efficiency nitride based light emitting diode by surface roughening. EP 2218114, international: H01L 33/00; H01L 33/22; H01L 33/20; H01L 33/32; European: H01L 33/22.

Claims (1)

A method of manufacturing a GaN-based LED, including the creation of a gallium nitride-based heterostructure, characterized in that a SiO ₂ antireflection optical coating is deposited on the GaN-n or GaN-p type light-emitting surface, and a microrelief is formed in it in the form of nano tips with a density of 10 ⁷ - 10 ⁸ pcs./cm ² .

Images