KR100918969B1 - Light emitting diode and method of forming the same - Google Patents

Abstract

PURPOSE: A light emitting diode and a method of forming the same are provided to allow light emitting diodes which are manufactured from one wafer to have uniform characteristics. CONSTITUTION: A light emitting diode(100) includes a substrate(101), a lower part semiconductor layer(110), an active layer, and a top semiconductor layer(130). The lower part semiconductor layer has a first sub-layer(111), a buffer layer(113), and a second sub-layer(115) which are laminated on the substrate in order. An active layer is formed on the lower part semiconductor layer, and the top semiconductor layer is formed on the active layer. The buffer layer has a lattice constant smaller than the first sub-layers and the second sub-layers.

Description

LIGHT EMITTING DIODE AND METHOD OF FORMING THE SAME

The present invention relates to a light emitting diode and a method of forming the same.

The present invention relates to a light emitting diode, and more particularly, to a light emitting diode having a high luminous efficiency and a method of forming the same.

The light-emitting diode (LED) is a kind of p-n junction diode, and is a semiconductor device using electroluminescence, which is a phenomenon in which a monochromatic light is emitted when a voltage is applied in a forward direction. The wavelength of light emitted from the light emitting diode is determined by the bandgap energy (Eg) of the material used. In the early days of the light emitting diode technology was developed that can mainly emit infrared light and red light. In 1993, Nika Chem. Nakamura discovered that GaN light-emitting diodes that can emit blue light can be produced using.

GaN light emitting diodes are generally formed by epitaxial growth of GaN on a sapphire substrate. Since the thermal expansion coefficient of the sapphire substrate is much different from that of the epitaxially grown GaN, warping of the sapphire substrate may occur during the GaN growth process. By bending of the sapphire substrate, the center may be convex. As the warpage of the sapphire substrate occurs, the contact between the susceptor with a heater and the sapphire substrate may be uneven. The nonuniformity of contact between these sapphire substrates causes a nonuniformity of the heat distribution transmitted from the heater, i.e., a difference in the heat distribution at the edges and the center of the substrate. Therefore, the non-uniformity of the heat transfer distribution causes non-uniform distribution of the dopant of the GaN electrode layer grown on the sapphire substrate, and thus acts as a factor for increasing the emission wavelength characteristic distribution of the InGaN active layer.

The present invention is to provide a method of forming a light emitting diode having a uniform characteristic distribution and the light emitting diode formed thereby.

A light emitting diode according to embodiments of the present invention is disclosed. The light emitting diode is a substrate; A lower semiconductor layer having a first lower layer, a buffer layer, and a second lower layer sequentially stacked on the substrate; An active layer on the lower semiconductor layer; And an upper semiconductor layer on the active layer. The buffer layer has a smaller lattice constant than the first lower layer and the second lower layer.

In example embodiments, the first lower layer and the second lower layer may be GaN, and the buffer layer may include atoms having a smaller shared radius than Ga.

A method of forming a light emitting diode according to embodiments of the present invention is disclosed. The method comprises forming a lower semiconductor layer on a substrate in the order of a first lower layer, a buffer layer and a second lower layer; And forming an active layer and an upper semiconductor layer in order on the lower semiconductor layer. Forming the buffer layer may include treating the lattice constant smaller than the first lower layer and the second lower layer.

According to the present invention, light emitting diodes formed in one wafer may have a uniform characteristic distribution.

Objects, other objects, features and advantages of the present invention will be readily understood through the following preferred embodiments associated with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosure may be made thorough and complete, and to fully convey the spirit of the invention to those skilled in the art.

In the present specification, when it is mentioned that a film is on another film or substrate, it means that it may be formed directly on another film or substrate or a third film may be interposed therebetween. In addition, in the drawings, the thicknesses of films and regions are exaggerated for effective explanation of technical contents. In addition, in various embodiments of the present specification, terms such as first, second, and third are used to describe various regions, films, and the like, but these regions and films should not be limited by these terms. do. These terms are only used to distinguish any given region or film from other regions or films. Thus, the film quality referred to as the first film quality in one embodiment may be referred to as the second film quality in other embodiments. Each embodiment described and illustrated herein also includes its complementary embodiment.

Referring to FIG. 1, a method of forming a light emitting diode 100 according to embodiments of the present invention will be described.

Referring to FIG. 1, a lower semiconductor layer 110 is formed on a substrate 101. The substrate 101 may be formed of one of sapphire, GaN, SiC, Si, ZrB ₂ and GaP. According to an embodiment of the present invention, the substrate 101 may be formed of sapphire. The lower semiconductor layer 110 may be formed in the order of the first lower layer 111, the buffer layer 113, and the second lower layer 115. The multilayer quantum well layer 120 and the upper semiconductor layer 130 may be sequentially formed on the lower semiconductor layer 110. The multilayer quantum well layer 120 may be InGaN, and the upper semiconductor layer 130 may be a semiconductor film (eg, p-GaN layer) having a p-type conductivity.

The first lower layer 111 may be formed of an undoped gallium nitride layer (hereinafter referred to as a u-GaN layer), and the second lower layer 115 may have an n-type semiconductor layer. (For example, an n-GaN layer). The u-GaN layer 111 may be formed by using the substrate 101 as a seed layer (liquid phase epitaxy (LPE), vapor phase epitaxy (VPE), and organometallic chemical vapor deposition (metal). organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) and the like can be formed using one of the epitaxial techniques. According to an embodiment of the present invention, the u-GaN layer 111 may be formed to a thickness of 2 to 3 micrometers. The second lower layer 115 may be formed through an epitaxial process using the first lower layer 111 and the buffer layer 113 as a seed layer, and according to an embodiment of the present invention, several micrometers It may be a silicon-doped GaN film (Si-doped GaN) formed to a thickness of.

The buffer layer 113 may be formed through an epitaxial process using the first lower layer 111 as a seed layer. The buffer layer 113 may be formed to have a smaller lattice constant than the first lower layer 111 and the second lower layer 115. As the lattice constant of the buffer layer 113 is smaller than that of the other, as shown in FIG. 2, the warpage shape of the substrate 101 may be reduced. In order to reduce the lattice constant of the buffer layer 113, the buffer layer 1130 may be formed to include atoms having a smaller covalent radius than Ga.

In one embodiment of the present invention, the atom having a smaller covalent radius than the Ga, for example, may be carbon or aluminum. The shared radius of Ga is 1.26 GHz and the shared radius of carbon is 0.77 Å. The carbon-containing GaN may be formed by using a carbon-containing source gas, for example, CCl ₄ or CBr ₄ , during a general GaN formation process. By applying the carbon source gas, the GaN buffer layer may be heavily doped with carbon. Referring to FIG. 3, the concentration of carbon doped in the GaN buffer layer 113 formed on the 3-inch sapphire wafer was 10 ²⁰ cm ³ or more according to an embodiment of the present invention. If the carbon concentration is 10 ¹⁸ cm ³ or more, the warpage of the sapphire substrate described above may be reduced.

4A and 4B, photoluminescence (PL) characteristics of a light emitting diode 100 formed on a 3 inch sapphire wafer according to an embodiment of the present invention of FIG. 3 will be described. Referring to FIG. 4A, if the buffer layer 113 is not applied, the standard deviation of the wavelength due to PL in the 3-inch wafer is 3.83 nm. However, when the buffer layer 113 is applied, the standard deviation is 1.96 nm. It was. That is, the warpage of the wafer during the formation of the lower semiconductor layer 110, the multilayer quantum well layer 120, and the upper semiconductor layer 130 by the buffer layer 113 is reduced. Accordingly, the uniformity of GaN and InGaN thin film characteristics for the lower semiconductor layer 110, the multilayer quantum well layer 120, and the upper semiconductor layer 130 is increased. In the non-application of the buffer layer 113, the yield at a maximum minimum difference of 7 nm of a product wavelength obtained from a 3 inch wafer was 50 to 60%. However, when the buffer layer 113 is applied, the yield of products having the same standard is improved to 99% or more. It became.

1 is a schematic view illustrating a light emitting diode and a method of forming the same according to embodiments of the present invention.

2 is a conceptual diagram illustrating the warpage phenomenon of the present invention.

3 is a graph measuring carbon concentration according to a depth of a lower semiconductor layer formed according to an embodiment of the present invention, which was measured by Secondary Ion Mass Spectrometry (SIMS).

4A is an emission wavelength analysis image when no buffer layer is used according to an embodiment of the present invention, and FIG. 4B is an emission wavelength analysis image when a buffer layer is used according to an embodiment of the present invention.

Claims (9)

Board; A lower semiconductor layer having a first lower layer, a buffer layer, and a second lower layer sequentially stacked on the substrate; An active layer on the lower semiconductor layer; And And an upper semiconductor layer on the active layer, wherein the buffer layer has a smaller lattice constant than the first lower layer and the second lower layer. The method of claim 1, Wherein the first lower layer and the second lower layer are GaN, and the buffer layer is GaN containing atoms having a smaller shared radius than Ga. The method of claim 2, An atom having a smaller share radius than the Ga comprises carbon. The method of claim 3, wherein The concentration of carbon is 10 ¹⁸ cm ³ or more. The method of claim 4, wherein The concentration of the carbon is 10 ²⁰ cm ³ or more light emitting diode. The method of claim 1, Wherein the first lower layer is undoped GaN, the second lower layer is GaN doped with N-type impurities, the active layer is an InGaN multilayer quantum well layer, and the upper semiconductor layer is GaN doped with P-type impurities. delete Forming a lower semiconductor layer on the substrate in the order of the first lower layer, the buffer layer and the second lower layer; And Forming an active layer and an upper semiconductor layer in order on the lower semiconductor layer; Forming the buffer layer includes treating the GaN with a high concentration of 10 ¹⁸ cm ³ or more so that the lattice constant is smaller than that of the first lower layer and the second lower layer, And the first lower layer and the second lower layer are GaN. The method of claim 8, Doping the carbon into the GaN comprises using CCl ₄ or CBr ₄ as the source gas during the GaN formation process.

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