JP2001210862A - Gallium nitride semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gallium nitride semiconductor light emitting element whose leak current is small, whose operation voltage is low, which is superior in light emitting efficiency and whose reproducibility is high. SOLUTION: In the gallium nitride semiconductor light emitting element having PN junction, a cap layer 500 constituted of an Mg doped BGaN semiconductor is formed on an active layer 400.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light emitting diode,
The present invention relates to a gallium nitride based semiconductor light emitting device used for a laser diode or the like.

[0002]

2. Description of the Related Art Gallium nitride-based semiconductors (GaN-based semiconductors) are used for light-emitting diode devices by realizing blue light emission which has been difficult for a long time. In this type of gallium nitride-based semiconductor, a P-type A
A cap layer composed of an lGaN semiconductor layer was formed, and a P-type GaN semiconductor layer was formed thereon. P-type AlGaN
Forming a cap layer made of a semiconductor layer contributes to improvement of luminous efficiency.

[0003]

However, P-type AlGa
When the Al concentration in the N semiconductor layer is reduced, the leak current tends to increase, and when the Al concentration is increased, the operating voltage tends to increase.

Also, trimethyl aluminum, which is generally used as a source of Al atoms, reacts with ammonia, which is a source of N atoms, in the gas phase, so that the ratio of Al and Ga in the AlGaN semiconductor layer can be reproducibly measured. There is also a problem that it is difficult to control.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a gallium nitride based semiconductor light emitting device having a small leakage current, a low operating voltage, excellent luminous efficiency, and high reproducibility. I have.

[0006]

A gallium nitride based semiconductor light emitting device according to the present invention is a gallium nitride based semiconductor light emitting device having a PN junction, wherein an Mg doped B
A cap layer made of a GaN semiconductor is formed.

[0007]

FIG. 1 is a schematic sectional view of a gallium nitride based semiconductor light emitting device according to an embodiment of the present invention.

The gallium nitride based semiconductor light emitting device according to the embodiment of the present invention is a gallium nitride based semiconductor light emitting device having a PN junction, wherein a cap layer 500 made of Mg-doped BGaN semiconductor is formed on an active layer 400. Have been.

The gallium nitride based semiconductor light emitting device is
It is manufactured by the following manufacturing process.

First, the sapphire substrate 100 is subjected to thermal cleaning. That is, the cleaning is performed by heating the sapphire substrate 100 to 1050 ° C. while supplying hydrogen in a reduced pressure MOCVD apparatus (a reduced pressure vapor phase growth apparatus).

Next, the temperature of the sapphire substrate 100 is set to 51
The temperature is lowered to 0 ° C., and ammonia and trimethylaluminum are supplied using nitrogen and hydrogen as carrier gases to form a low-temperature AlN buffer layer 200 on the surface of the sapphire substrate 100. This AlN buffer layer 200 is about 200 °.

Next, the temperature of the sapphire substrate 100 is set to 10
The temperature is raised to 00 ° C., and ammonia and trimethylgallium are flowed using the carrier gas. At this time, the silicon-doped GaN semiconductor layer 300 as the N-type GaN semiconductor layer was simultaneously formed using silicon as the N-type impurity by about 1.2 μm.
Let it grow.

Next, the temperature of the sapphire substrate 100 is set to about 7
The temperature is lowered to 30 ° C., and the active layer 400 made of InGaN multiple quantum wells (MQW) is placed on the Si-doped GaN layer 300 by about 40 minutes while intermittently flowing trimethylindium.
Grow 0 °.

Further, the temperature of the sapphire substrate 100 is set to 9
BG doped with magnesium raised to 00 ° C
The cap layer 500, which is an aN semiconductor layer, is
Grow on zero. This cap layer 500 is about 100
厚 thickness. The content of B in the cap layer 500 is 2%.

Next, the temperature of the sapphire substrate 100 is set to 85.
The temperature was lowered to 0 ° C., magnesium was added as an impurity to the carrier gas, and Mg-doped G was used as a P-type GaN semiconductor layer.
The aN semiconductor layer 600 is grown to about 0.2 μm.

Next, the temperature of the sapphire substrate 100 is set to 80
0 ° C., and the pressure in the reduced pressure MOCVD apparatus was 6650 Pa
(50 torr). At the same time, the atmosphere of the mixed gas containing hydrogen such as ammonia is rapidly reduced in pressure
The atmosphere in the CVD apparatus is switched to nitrogen gas which is an inert gas.

Then, using a nitrogen gas as a carrier gas and flowing trimethyl zinc, a Zn film 700 having a thickness of several tens of degrees is formed. Then, the temperature of the sapphire substrate 100 is set to about 100 in this state, that is, in a nitrogen atmosphere.
To below ℃.

After that, the sapphire substrate 100 on which the Zn film 700 is formed is put into a vacuum deposition apparatus, and ITO containing 10% of SnO ₂ is heated and evaporated by an electron gun to obtain a current diffusion layer having a thickness of about 0.5 μm. The ITO film 800 as a layer is Zn
It is formed over the film 700. Sapphire substrate 10 at this time
The temperature of 0 was 200 ° C.

Next, a part of the ITO film 800 is dry-etched to expose a part of the Si-doped GaN layer 300. The exposed Si-doped GaN semiconductor layer 300
A P-type electrode 920 is formed on a part of the ITO film 800 as a P-type electrode 910. Both electrodes 910 and 920 are made of Ti
/ Au thin film deposited by about 500/5000 °.

The gallium nitride based semiconductor light emitting device manufactured in this way has an operating voltage of 3.6 at a current of 20 mA.
V, sufficiently low, and luminous efficiency is Mg-doped P-type AlGaN
It was confirmed that there was no inferiority to a conventional gallium nitride based semiconductor light emitting device using a semiconductor layer as a cap layer. Also, it was confirmed that the leak current was 10 μA or less at 5 V, which is a level that poses no practical problem.

In the above-described embodiment, the ITO film 800 as a current diffusion layer is formed by a vacuum deposition method. However, even if the ITO film 800 is not formed, Ni / Au
If a thin film or an AuGe / Au thin film is used as the translucent auxiliary electrode, it is possible to form a gallium nitride based semiconductor light emitting device equivalent to the conventional one, although the light extraction efficiency is slightly reduced.

[0022]

According to the gallium nitride based semiconductor light emitting device of the present invention, in the gallium nitride based semiconductor light emitting device having a PN junction, a cap layer made of Mg-doped BGaN semiconductor is formed on the active layer.

Such a gallium nitride based semiconductor light emitting device has a sufficiently low operating voltage of 3.6 V at a current of 20 mA, and it has been confirmed that the luminous efficiency is comparable to that of the conventional device. Also, it was confirmed that the leak current was 10 μA or less at 5 V, which is a level that poses no practical problem. Further, a gallium nitride based semiconductor light emitting device having high reproducibility was obtained.

The content of B in the cap layer made of the Mg-doped BGaN semiconductor is desirably 0.1% or more and 5.0% or less, as can be seen from Table 1 below. Is 1 as can be seen from Table 2 below.
Desirably, it is 0 ° or more and 200 ° or less.

Table 1 Difference between leakage current and operating voltage due to difference in B content in cap layer made of Mg-doped BGaN semiconductor having a thickness of 100 ° B (%) Leak current (μA) Operating voltage (V) 1 100 3.2 1.05 3.4 2.0 2 3.6 5.0 0 0 4.5

Table 2 Difference between leakage current and operating voltage due to difference in thickness of cap layer made of Mg-doped BGaN semiconductor containing 1% of B

When the B content is less than 0.1%, the leakage current is increased, and when it is more than 5%, the crystallinity is deteriorated, so that the operating voltage is increased and the luminous efficiency is also deteriorated. Was. Also, it was confirmed that when the thickness of the cap layer was 10 ° or less, the leak current increased, and when the thickness was 200 ° or more, the operating voltage increased and the luminous efficiency tended to deteriorate. The details of this theoretical reason are unclear, but B
It is considered that there is a critical composition and a critical film thickness for obtaining a good crystal due to the difference in the size of atoms between Ga and Ga.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a gallium nitride based semiconductor light emitting device according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 100 sapphire substrate 200 AlN buffer layer 300 Si-doped GaN layer 400 active layer 500 cap layer 600 Mg-doped GaN layer 700 Zn layer 800 N-type electrode 900 P-type electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F041 AA03 AA08 AA41 CA34 CA40 CA46 CA49 5F073 AA42 AA74 AA89 CA07 CB05 DA05 DA24 EA07 EA23

Claims (2)

[Claims] 1. A gallium nitride based semiconductor light emitting device having a PN junction, wherein a cap layer made of a Mg-doped BGaN semiconductor is formed on an active layer. 2. The B content of the cap layer made of the Mg-doped BGaN semiconductor is 0.1% or more and 5.0% or less, and the thickness of the cap layer is 10 ° or more and 200 ° or less. The gallium nitride based semiconductor light emitting device according to claim 1.