JP2560963B2 - Gallium nitride compound semiconductor light emitting device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device using a gallium nitride compound semiconductor.

[0002]

2. Description of the Related Art GaN, GaAlN, InGaN, In
Since gallium nitride-based compound semiconductors such as AlGaN have a direct transition and the bandgap changes up to 1.95 eV-6 eV, they are regarded as promising materials for light emitting devices such as light emitting diodes and laser diodes. At present, in a light emitting device using this material, a so-called MIS in which a high-resistance i-type gallium nitride-based compound semiconductor doped with a p-type dopant is stacked on an n-type gallium nitride-based compound semiconductor
Blue light emitting diodes with a structure are known.

As a light-emitting element having a MIS structure, for example, in JP-A-4-10665, JP-A-4-10666 and JP-A-4-10667, an n-type Ga _Y is disclosed.
On the Al _1-Y N, technique of laminating an i-type _Ga doped with Si and Zn _{Y Al 1-Y} N is disclosed.
According to these techniques, Si and Zn are converted into Ga _Y Al _1-Y.
By doping N to form an i-type light emitting layer, the emission color of the light emitting element can be made white.

[0004]

However, as in the above technique, a high-resistance i-type doped with Zn as a p-type dopant and further doped with Si as an n-type dopant.
A MIS structure light-emitting element having a type Ga _Y Al _1-YN layer as a light-emitting layer has low luminance and light-emission output, and is still insufficient for practical use as a light-emitting element.

Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to improve the brightness and the light emission output of a light emitting device by using a gallium nitride-based compound semiconductor having a pn junction. It is an attempt to improve.

[0006]

The gallium nitride system of the present invention
The compound semiconductor light-emitting device is an n-type gallium nitride compound
Between the conductor and the p-type gallium nitride compound semiconductor layer,
The light emitting layer of the nitride semiconductor layer containing indium and gallium
That the light emitting layer is doped with Si and Zn.
Characterize. In particular, the gallium nitride-based compound semiconductor of the present invention
The body light emitting device includes Zn and Si-doped indium.
A structure including a light emitting layer of a nitride semiconductor layer containing gallium,
As a result, the conventional MIS structure light emitting device
And dramatically improve the emission characteristics of the double hetero structure.
That was successful.

In the gallium nitride-based compound semiconductor light emitting device of the present invention, the n-type and p-type gallium nitride-based compound semiconductor layers are GaN, GaAlN, InGaN and InA.
A gallium nitride-based compound semiconductor containing gallium nitride, such as lGaN, may be formed of, for example, Si, Ge, Se, Te if it is n-type
Is a layer grown to show n-type characteristics by being doped with an n-type dopant such as z.
A layer grown by doping with a p-type dopant such as g, Cd, Be, or Ca to exhibit p-type characteristics. In the case of an n-type gallium nitride-based compound semiconductor, it has a property of becoming n-type even if it is not doped. Further, in the case of a p-type gallium nitride compound semiconductor layer, as a means for further reducing the resistance of the p-type gallium nitride compound semiconductor layer, an annealing treatment disclosed in Japanese Patent Application No. 3-357046 previously filed by us is performed. May be.

A light emitting layer doped with Zn and Si
It is _preferably represented by a composition formula of In x _{Ga 1-x} N
It In this composition formula, the value of X is preferably adjusted within the range of 0 <X <0.5. Nitride half of this composition formula
By setting the X value of the conductor layer to be greater than 0, the emission color is in the purple region. As the X value increases, the emission color shifts from the short wavelength side to the long wavelength side, and can be changed to red when the X value is around 1. However, when the X value is 0.5 or more, it is difficult to obtain InGaN having excellent crystallinity and it is difficult to obtain a light emitting device having excellent light emitting efficiency. Therefore, the X value is preferably less than 0.5.

Further , indium and gallium which are light emitting layers
The concentrations of Zn and Si contained in the nitride semiconductor layer containing Si are both 1 × 10 ¹⁷ / cm ³ to 1 × 10 ²¹ / c.
It is preferable to adjust to the range of m ³ . 1 x 10 ¹⁷ /
If it is less than cm ^3, it is difficult to obtain sufficient emission intensity,
When it is more than 1 × 10 ²¹ / cm ³ , the emission intensity tends to decrease. Further, by making the Si concentration higher than the Zn concentration, InGaN can be preferably made to be n-type.

[0010]

In FIG. 1, an n-type In0.15Ga0.85N layer doped with Zn at 1 × 10 ¹⁸ / cm ³ and Zn at 1 × 1
0 ¹⁹ / cm ³ and 5 × 10 ¹⁹ / cm ³ Si-doped n-type In0.15Ga0.85N layer and He-C.
The photoluminescence (PL) was measured at room temperature by irradiating d laser, and their emission intensities are compared and shown.
The spectral intensity of the InGaN layer doped with only Zn is shown by enlarging the actual intensity ten times. As shown in this figure, n-type InGaN doped only with Zn
The PL spectrum (b) of the above and the PL spectrum (a) of n-type InGaN doped with Si and Zn are both 49
It has its main emission peak at 0 nm. However, the emission intensity of (a) is 10 times or more higher. this is,
It is presumed that the donor concentration is increased by further doping Si into Zn-doped InGaN, and the emission intensity is increased by the donor-acceptor pair emission.
This is because non-doped InGaN has an electron carrier concentration of approximately 1 × 10 ¹⁷ / cm ³ to 1 ×, depending on the growth conditions.
It exhibits an n-type of about 10 ²² / cm ³ . This indicates that a certain number of donors remain in InGaN in a non-doped state. Therefore, when Zn is doped into this non-doped InGaN, pair emission of the residual donor and the donor-acceptor of the doped Zn acceptor appears as blue emission. However, as described above, the electron carrier concentration due to the residual donor varies up to about 1 × 10 ¹⁷ to 1 × 10 ²² / cm ³ depending on the growth condition, and the I of a constant donor concentration is constant with good reproducibility.
It was difficult to obtain nGaN. Therefore, a new S
The effect of Si doping is to dope i to increase the donor concentration and to obtain a stable and reproducible constant donor concentration. In fact, by doping Si,
It was found that the electron carrier concentration of about 1 × 10 ¹⁸ / cm ³ increased by one digit to 2 × 10 ¹⁹ / cm ³ , and the donor concentration increased. Therefore, it is presumed that the amount of Zn to be doped can be increased by the amount of increased donors, and the blue emission intensity is increased by increasing the number of pair emission of donor / acceptor.

The gallium nitride-based compound semiconductor light-emitting device of the present invention comprises an n-type gallium nitride-based compound semiconductor and a p-type nitride.
Indium and gallium between the gallium compound semiconductor
A semiconductor light emitting device having a nitride semiconductor layer containing
By doping the light emitting layer with Si and Zn,
The light emission efficiency and the light emission intensity can be remarkably improved to 100 times or more as compared with the conventional light emitting element having the MIS structure in which the light emitting layer is i-type GaAlN doped with Si and Zn.

[0012]

EXAMPLES A method of manufacturing the light emitting device of the present invention by the metal organic chemical vapor deposition method will be described below.

Example 1 A well-cleaned sapphire substrate was set in a reaction vessel,
After sufficiently replacing the inside of the reaction vessel with hydrogen, the temperature of the substrate is raised to 1050 ° C. while flowing hydrogen to clean the sapphire substrate.

Then, the temperature is lowered to 510 ° C., hydrogen is used as a carrier gas, and ammonia and TMG are used as a source gas.
(Trimethylgallium), a buffer layer made of GaN is grown on the sapphire substrate with a thickness of about 200 Å.

After the growth of the buffer layer, only TMG is stopped and the temperature is raised to 1030.degree. When the temperature reached 1030 ° C., TMG and ammonia gas were used as the source gas, and silane gas was used as the dopant gas, and Si was added at 1 × 10 ²⁰ / c.
An m ³ -doped n-type GaN layer is grown to 4 μm.

After the growth of the n-type GaN layer, the source gas and the dopant gas are stopped, the temperature is set to 800 ° C., the carrier gas is switched to nitrogen, TMG, TMI (trimethylindium) and ammonia are used as the source gases, and silane gas is used as the dopant gas. Using DEZ (diethyl zinc), S
i is 5 × 10 ¹⁹ / cm ³ and Zn is 1 × 10 ¹⁹ / cm 3.
^3- doped n-type In0.15Ga0.85N layer 10
Grow to 0 angstrom.

Next, stop the source gas and the dopant gas,
The temperature is again raised to 1020 ° C. and T is used as a source gas.
MG and ammonia, Cp2Mg as a dopant gas
(Cyclopentadienyl magnesium) and Mg
Of a p-type GaN layer doped with 2 × 10 ²⁰ / cm ^{3 of} 0.2.
Grow 8 μm.

After the growth of the p-type GaN layer, the substrate was taken out of the reaction container and then annealed at 700 in a nitrogen atmosphere.
Anneal at 20 ° C for 20 minutes to obtain the top p-type GaN
The resistance of the layer is further reduced.

A part of the p-type GaN layer and the n-type In0.15Ga0.85N layer of the wafer thus obtained is removed by etching to expose the n-type GaN layer, and the p-type GaN layer and the n-type GaN layer. After forming an ohmic electrode on the GaN layer and cutting it into chips of 500 μm square, a light emitting diode was produced by a conventional method.
In A, the emission was 300 μW, the brightness was 900 mcd (millicandela), and the emission wavelength was 490 nm.

Example 2 In Example 1, the n-type In0.15Ga0.85N layer had a Si concentration of 2 × 10 ²⁰ / cm ³ and a Zn concentration of 5 × 1.
0 addition to the ¹⁹ / cm ³ is where to obtain a blue light-emitting diodes in the same manner, the light emission output in 20 mA 300 microns
W, luminance was 920 mcd, and emission wavelength was 490 nm.

Example 3 In Example 1, the n-type In0.15Ga0.85N layer had a Si concentration of 5 × 10 ¹⁸ / cm ³ and a Zn concentration of 1 × 1.
A blue light emitting diode was obtained in the same manner except that it was 0 ¹⁸ / cm ^3, and the emission output was 280 μm at 20 mA.
W, brightness 850 mcd, and emission wavelength 490 nm.

Example 4 In Example 1, the In molar ratio of n-type InGaN was changed to I
A blue light emitting diode was obtained in the same manner except that n0.25Ga0.75N was obtained. At 20 mA, a light emission output of 250 μW, a luminance of 1000 mcd, and an emission wavelength of 510 n
It was m.

Comparative Example 1 In Example 1, Zn concentration was 1 × 1 without Si doping.
Zn-doped In0.15Ga0.85 of 0 ¹⁸ / cm ³
When a light emitting diode was made in the same manner except that N was grown, a light emission output of 180 μW and a brightness of 4 at 20 mA.
The emission wavelength was 490 nm.

[Comparative Example 2] Si, Zn-doped n-type In0.15GaO.
In the process of growing the 85N layer, TM is used as the source gas.
G, ammonia, silane gas as dopant gas, DEZ
By using Si for 1 × 10 ¹⁸ / cm ³ and Zn for 1 × 1
An i-type GaN layer doped with 0 ²⁰ / cm ³ is grown.
After growing the i-type GaN layer, a part of the i-type GaN layer is similarly etched to expose the n-type GaN layer, electrodes are provided on the n-type GaN layer and the i-type GaN layer, and a MIS structure light emitting diode is formed. rollers and was, emission output 1 at 20mA
It had only μW and a brightness of 0.1 mcd.

[0025]

As described above, the gallium nitride-based compound semiconductor light-emitting device of the present invention is composed of indium and gallium.
A light emitting layer of a nitride semiconductor layer containing
By doping i and Zn, the conventional MIS structure is
Not to mention the light emitting element of the structure, the light emission of the double hetero structure
Even if it is an element, it can not be imagined at all, it has been dramatically improved
Achieves luminous efficiency and luminous strength. Moreover, the main emission wavelength can be freely adjusted from red to purple by changing the molar ratio of In in InGaN, and its industrial utility value is great.

[Brief description of drawings]

FIG. 1 InGaN layer doped only with Zn (b)
3A and 3B are diagrams showing a comparison of photoluminescence intensity at room temperature between InGaN layer (a) doped with Zn and Si.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-4-10665 (JP, A) JP-A-4-10666 (JP, A) JP-A-4-10667 (JP, A) JP-A-3- 252175 (JP, A) JP 4-252175 (JP, A) JP 4-236478 (JP, A) JP 4-199752 (JP, A) JP 59-228776 (JP, A)

Claims (1)

(57) [Claims] 1. An n-type gallium nitride-based compound semiconductor layer,
Between the p-type gallium nitride-based compound semiconductor layer, indium
And a light emitting layer of a nitride semiconductor layer containing gallium.
A gallium nitride-based compound semiconductor light-emitting device having an optical layer doped with Si and Zn .