JPH03252176A - Light emitting element of gallium nitride compound semiconductor - Google Patents

Abstract

PURPOSE:To increase blue light emitting intensity of a light emitting diode by forming a double layer structure of a low carrier concentration layer and a high carrier concentration layer sequentially from the side of connecting an N-type layer to an l-type layer. CONSTITUTION:A sapphire board 1 is vapor etched, an AlN buffer layer 2 is formed, a high carrier concentration layer 3 made of GaN is formed, and then an N<+> type low carrier concentration layer 4 made of GaN is formed. Then, an I-type layer 5 made of GaN is formed.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a gallium nitride compound semiconductor light emitting device that emits blue light.

[Prior art]

Conventionally, blue light emitting diodes using GaN-based compound semiconductors are known. The GaN-based compound semiconductor is attracting attention because it has high luminous efficiency due to direct transition, and because it emits blue light, which is one of the three primary colors of light. A light emitting diode using such a GaN-based compound semiconductor is produced by growing an N layer made of an N-conductivity type GaN-based compound semiconductor on a sapphire substrate directly or with a buffer layer made of aluminum nitride interposed therebetween. It has a structure in which a single layer of I-type GaN-based compound semiconductor is grown on top of the N layer by doping P-type impurities (Japanese Unexamined Patent Application Publication No. 1983-1992).
2-119196, JP-A-63-188977).

[Problem to be solved by the invention]

However, the light emitting intensity of the light emitting diode with the above structure is still not sufficient, and improvements are desired. Therefore, an object of the present invention is to improve the blue light emission intensity of a GaN-based compound semiconductor light emitting diode.

[Means to solve the problem]

The present invention relates to an N-type gallium nitride compound semiconductor (Amc
at-xN (including X=O), and an I-type gallium nitride compound semiconductor (Al
xGar-xN (including It has a double layer structure. Furthermore, the carrier concentration of the above-mentioned low carrier concentration N layer is lX10
It is desirable that the film thickness be 0.5 to 2 mm with a film thickness of 14 to 1X10"/cut. If the carrier concentration exceeds IX1017/cr1, the emission intensity will decrease, which is undesirable.
If it is less than 0''/el+!, the series resistance of the light emitting element will become too high and heat will be generated when current is passed, which is undesirable.
If the film thickness is 2 sails or more, the series resistance of the light emitting element will become too high and heat will be generated when current is passed, which is undesirable.
．． If it is less than 5-5, the luminescence intensity will decrease, which is not desirable. Furthermore, the carrier concentration of the high carrier concentration 84 layer is 1×10
+7 to lXl0"/el+!, and the film thickness is preferably 2 to 10 cm. The carrier concentration is lXl0"/ca! If it is more than that, the crystallinity will deteriorate, which is undesirable, and I×10'7/d
If it is below, the series resistance of the light emitting element will become too high and heat will be generated when current is passed, which is not desirable. Also, the film thickness is 10μs
If it is more than that, the substrate will be curved, which is undesirable, and if the film thickness is less than 2 mm, the series resistance of the light emitting element will become too high, causing heat to be generated when current is passed, which is undesirable.

[Operation and effects of the invention]

The present invention makes it possible to increase the blue light emission intensity of a light emitting diode by forming a double layer structure of a low carrier concentration N layer and a high carrier concentration 84 layers in order from the side where the N layer is joined to the first layer. Ta. That is, the electrical resistance of the entire N layer can be reduced by the high carrier concentration 84 layer, the series resistance of the light emitting diode can be reduced, and the heat generation of the light emitting diode can be suppressed. In addition, the N layer that is connected to the first layer should have a low carrier concentration, that is, the Ga
By highly purifying N, it is possible to suppress the impurity atom concentration that degrades blue light emission in the light emitting region (one layer and its vicinity). The above effects improved the blue light emission intensity.

【Example】

The present invention will be described below based on specific examples. In FIG. 1, a light emitting diode 1o has a sapphire substrate 1 on which a buffer layer 2 of 500 AIN is formed. On the buffer layer 2, a high carrier concentration N1 layer 3 made of GaN with a film thickness of 22 um and a low carrier concentration N layer 4 made of GaN with a film thickness of 1.5 μm are formed in order. , a layer 5 made of GaN having a thickness of 0.2 mm is formed on the low carrier concentration N layer 4. Then, an electrode 7 formed of aluminum connected to the first layer 5 and a high carrier concentration 8
An electrode 8 made of aluminum and connected to the four layers 3 is formed. Next, a method for manufacturing the light emitting diode 10 having this structure will be described. The light emitting diode 10 was manufactured by vapor phase growth using an organometallic compound vapor phase growth method (hereinafter referred to as rMOVPfi J). The gases used were NHs, carrier gas H2, and trimethylgallium (Ga(CHs)s) (rTM
G J) and trimethylaluminum (AI (CH
, ), ) (hereinafter referred to as rTMAJ) and silane (SiH
) and diethylzinc (hereinafter referred to as rDEZJ). First, a single-crystal sapphire substrate 1 having an a-plane main surface that has been cleaned by organic cleaning and heat treatment is mounted on a susceptor placed in a reaction chamber of a MOVPE apparatus. Next, the sapphire substrate 1 was subjected to vapor phase etching at a temperature of 1100° C. while flowing N2 into the reaction chamber at a flow rate of 2β/min at normal pressure. Next, reduce the temperature to 400°C and add 26j' of N2.
/min, 101 NHs! /min, TMA 1.8x 10
Buffer layer 2 of AffN supplied at -5MoJl//min
was formed to a thickness of about 500 people. Next, maintain the temperature of the sapphire substrate 1 at 1150t,
N2 at 20Il/min, N layer 5 at 101/min, TMG at 1
．． Silane (Si) diluted to 0.86 ppm with 7X 10-' mol/min, 1. ) was supplied for 30 minutes at a rate of 200 m1/min, the film thickness was 2.2 m, and the carrier concentration was 1 m.
．． A high carrier concentration N4 layer 3 made of GaN of 5×10"/Cl1l was formed. Subsequently, the temperature of the sapphire substrate 1 was maintained at 1150°C, and N2 was supplied at 201!/min, NH at 101/min, and TMG at 101/min. It was supplied for 20 minutes at a rate of 1°7×10−' morph, with a film thickness of about 1.5 μs and a carrier concentration of 1×10”/ca! G of
A low carrier concentration N layer 4 made of aN was formed. Next, the sapphire substrate 1 was heated to 900°C and N3 was heated to 20°C.
1/min, NH, 101/min, TMG 1.7X 10
-' morph and DEZ was supplied for 2 minutes at a rate of 1.5×10 -' morph to form one layer 5 made of GaN with a film thickness of 0.2 μs. In this way, a multilayer structure as shown in FIG. 2 was obtained. Next, as shown in FIG. 3, a SlO□ layer 11 was formed on the first layer 5 by sputtering to a thickness of 2,000 layers. Next, a photoresist 12 is placed on the SiO□ layer 11.
was coated, and the photoresist 12 was formed by photolithography into a pattern in which the photoresist at the electrode formation site for the high carrier concentration N3 layer 3 was removed. Next, as shown in FIG. 4, the SiO□ layer 11 not covered with the photoresist 12 was removed using a hydrofluoric acid etching solution. Next, as shown in FIG.
1 layer 5 in a portion not covered by the iDx layer 11, a low carrier concentration N layer 4 below it, and a high carrier concentration N1 layer 3
A part of the upper surface of the
．． 44W/7, CCβ2F2 gas was supplied at a rate of 10 ml/min for dry etching, and then dry etching was performed with Ar. Next, as shown in FIG.
02 layer 11 was removed with hydrofluoric acid. Next, as shown in FIG. 7, an AI layer 1 is placed on the entire upper surface of the sample.
3 was formed by vapor deposition. Then, a 7 photoresist 14 was coated on the A1 layer 13, and the photoresist 14 was patterned into a predetermined shape by photolithography so that electrode portions for the high carrier concentration N+ layer 3 and the 1 layer 5 remained. . Next, as shown in FIG. 7, using the photoresist 14 as a mask, the exposed portion of the lower AI layer 13 is etched with a nitric acid-based etching solution, the photoresist 14 is removed with acetone, and the high carrier concentration N+ layer 3 is etched. Electrode 8.1 Electrode 7 of layer 5 was formed. In this way, Mis(Metal-1
It is possible to manufacture a gallium nitride-based light emitting device having a nsuIator Sem1 conductor) structure. When the light emitting intensity of the light emitting diode 10 manufactured in this manner was measured, it was found to be Q, 2 mcd. This is simply one layer and a carrier concentration of 5x 10”/c
Compared to a conventional light-emitting diode in which RL and an N layer with a thickness of 4 μs were connected, the light emission intensity was improved four times. Furthermore, when the light emitting surface was observed, it was also observed that the number of light emitting points was increasing. For comparison, the above samples were manufactured in which the carrier concentration of the low carrier concentration N layer 4 was varied, and the emission intensity and emission spectrum were measured. The results are shown in FIG. As the carrier concentration increases, the emission intensity decreases,
Moreover, it can be seen that the emission wavelength stops shifting toward the red side. This means that silicon, which is a doping element, is diffused or mixed into layer 5 as an impurity element.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the structure of a light emitting diode according to a specific embodiment of the present invention, FIGS. 2 to 7 are cross-sectional views showing the manufacturing process of the light emitting diode of the same embodiment, and FIG. The figure is a measurement diagram showing the relationship between the carrier concentration of the low carrier concentration N layer, the emission intensity, and the emission wavelength. 10 Light emitting diode 1 Sapphire substrate 2 Buffer layer 3 High carrier concentration N layer 4 Low carrier concentration N
Layers 51 layers 7.8 electrodes

Claims (1)

[Claims] N-type gallium nitride compound semiconductor (Al_xGa_1
____xN;
In a gallium nitride compound semiconductor light emitting device having an I layer consisting of _xGa_1_-_xN; A light emitting device characterized by having a double layer structure with a ^+ layer.