JP3335974B2 - Gallium nitride based semiconductor light emitting device and method of manufacturing the same - Google Patents

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 and a method for manufacturing the same.

[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 made 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.

The active layer usually contains In (indium) and grows at a relatively low temperature of 700 to 800.degree. For this reason, it has been confirmed that when the temperature of crystal growth of the semiconductor layer formed thereon becomes higher than 900 to 950 ° C., the active layer is degraded and the luminous efficiency is reduced. I have.

However, since the P-type AlGaN semiconductor layer is originally preferably grown at a high temperature of 1000 ° C. or higher,
If the crystal is grown at a lower temperature than that, the basic physical properties such as carrier concentration and mobility change each time the crystal grows, and the reproducibility becomes poor. As a measure for ensuring reproducibility, there is an extremely slow growth rate or the like, but it is not suitable for mass production.

The present invention has been made in view of the above circumstances, and provides a gallium nitride based semiconductor light emitting device having a small leakage current, a low operating voltage, excellent luminous efficiency, and high reproducibility, and a method of manufacturing the same. It is intended to be.

[0007]

A gallium nitride based semiconductor light emitting device according to the present invention is a gallium nitride based semiconductor light emitting device in which an N-type GaN semiconductor layer, an active layer and a P-type GaN semiconductor layer are sequentially laminated. An undoped cap layer is formed between the active layer and the P-type GaN semiconductor layer, and the cap layer is a superlattice layer made of AlN and GaN.

[0008]

FIG. 1 is a schematic sectional view of a gallium nitride based semiconductor light emitting device according to an embodiment of the present invention, and FIG. 2 is a schematic enlarged view of a main part of the gallium nitride based semiconductor light emitting device according to the present invention. It is sectional drawing.

A gallium nitride-based semiconductor light emitting device according to an embodiment of the present invention includes a Si-doped GaN semiconductor layer 300 as an N-type GaN semiconductor layer, an active layer 400 and a P-type Ga
A gallium nitride-based semiconductor light emitting device in which an Mg-doped GaN semiconductor layer 600 as an N semiconductor layer is sequentially stacked, wherein the active layer 400 and the Mg-doped GaN semiconductor layer 60 are stacked.
0 and the cap layer 50 not doped
0 is formed, and the cap layer 500 is made of AlN
And a GaN superlattice layer.

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 to 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 an active layer 400 composed of a multiple quantum well (MQW) of N-type GaN and N-type InGaN is grown on the Si-doped GaN layer 300 by about 400 ° while intermittently flowing trimethylindium.

Further, the temperature of the sapphire substrate 100 is set to 8
G increased to 50 ° C. without magnesium doping
The cap layer 500, which is an aN semiconductor layer, is
Grow on zero. The cap layer 500 is made of AlN 510 and GaN 520 which are not doped with magnesium.
A superlattice layer consisting of
The thickness of the aN is 90 °, and four layers of AlN and GaN (total thickness of 400 °) are provided.

Next, magnesium is added as an impurity to the carrier gas to grow a Mg-doped GaN semiconductor layer 600 as a P-type GaN semiconductor layer by about 0.2 μm.

In the above-described process, the Si-doped GaN
The temperature of the sapphire substrate 100 during the crystal growth of the semiconductor layer 300 is 1000 ° C., the temperature of the sapphire substrate 100 during the crystal growth of the active layer 400 is 730 ° C., and the cap layer 500A
Temperature of sapphire substrate 100 at the time of crystal growth of 850 ° C.
It has become. That is, the cap layer 500A which is a P-type GaN semiconductor layer formed on the cap layer 500A
Temperature at the time of crystal growth (850 ° C.) of the active layer 400 is higher than the temperature at the time of crystal growth of the active layer 400 (730 ° C.), and N-type Ga
The temperature is lower than the temperature (1000 ° C.) at the time of crystal growth of the Si-doped GaN semiconductor layer 300 as the N semiconductor layer.

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 evaporation 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 3.4 at a current of 20 mA.
Very low V 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. In addition, it was confirmed that the leak current was 10 μA or less at 5 V, which is a level having no practical problem.

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

The gallium nitride based semiconductor light emitting device according to the present invention is a gallium nitride based semiconductor light emitting device in which an N-type GaN semiconductor layer, an active layer and a P-type GaN semiconductor layer are sequentially laminated. An undoped cap layer is formed between the semiconductor layer and the P-type GaN semiconductor layer, and the cap layer is a superlattice layer made of AlN and GaN.

As described above, the cap layer is made of AlN and G
In the case of a superlattice layer composed of aN, a gallium nitride-based semiconductor light-emitting device having low leakage current, low operating voltage, excellent luminous efficiency, and high reproducibility could be obtained.

In particular, the P formed on the cap layer
When the temperature at the time of crystal growth of the n-type GaN semiconductor layer is higher than the temperature at the time of crystal growth of the active layer and lower than the temperature at the time of crystal growth of the N-type GaN semiconductor layer, the leakage current is small and the operating voltage is low, In addition, it was confirmed that the gallium nitride-based semiconductor light emitting device had high reproducibility without lowering the luminous efficiency.

The thickness of the cap layer is 100.degree.
When the temperature is 1000 ° C. or less, a gallium nitride based semiconductor light emitting device having a small leakage current and a low operating voltage can be manufactured with good reproducibility.

[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.

FIG. 2 is a schematic enlarged sectional view of a main part of the gallium nitride based semiconductor light emitting device according to 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 Continuation of front page (56) References JP-A-9-129926 (JP, A) JP-A-11-330554 (JP, A) JP-A-11-54847 (JP, A) JP-A-11-548 68159 (JP, A) JP-A-10-200214 (JP, A) JP-A-11-354846 (JP, A) JP-A-9-64419 (JP, A) JP-A-10-12923 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 33/00 H01S 5/323 JICST file (JOIS)

Claims (4)

(57) [Claims] 1. An N-type GaN semiconductor layer, an active layer, and a P-type G
In a gallium nitride based semiconductor light emitting device in which an aN semiconductor layer is sequentially stacked, an undoped cap layer is formed between the active layer and the P-type GaN semiconductor layer, and the cap layer is formed of AlN and A gallium nitride-based semiconductor light emitting device, which is a superlattice layer made of GaN. 2. The gallium nitride based semiconductor light emitting device according to claim 1, wherein the thickness of the cap layer is 100 ° or more and 1000 ° or less. 3. A P-type G formed on the cap layer.
3. The temperature according to claim 1, wherein a temperature during the crystal growth of the aN semiconductor layer is higher than a temperature during the crystal growth of the active layer and lower than a temperature during the crystal growth of the N-type GaN semiconductor layer. Gallium nitride based semiconductor light emitting device. 4. An N-type GaN semiconductor layer, an active layer, and a P-type G
In the method for manufacturing a gallium nitride based semiconductor light emitting device in which an aN semiconductor layer is sequentially stacked, an undoped cap layer is formed between the active layer and the P-type GaN semiconductor layer, and the cap layer is , AlN and GaN
Wherein the temperature at the time of crystal growth of the P-type GaN semiconductor layer formed on the cap layer is higher than the temperature at the time of crystal growth of the active layer, and the N-type GaN
A method for manufacturing a gallium nitride based semiconductor light emitting device, wherein the temperature is lower than the temperature at the time of crystal growth of a semiconductor layer.