JPH06260680A - Gallium nitride compound semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To improve luminance and light emitting output of a light emitting element by using a p-n junction gallium nitride compound semiconductor. CONSTITUTION:An n-type InxGa1-x (N (where X is set to a range of 0<X<1) doped with Si and Zn is provided as a light emitting layer between an n-type gallium nitride compound semiconductor layer and a p-type gallium nitride compound semiconductor layer.

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 from 1.95 eV to 6 eV, they are regarded as promising materials for light emitting devices such as light emitting diodes and laser diodes. At present, a light emitting device using this material is a so-called MIS in which a high-resistance i-type gallium nitride compound semiconductor doped with a p-type dopant is stacked on an n-type gallium nitride 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, n-type Ga _Y is disclosed.
_I- type G doped with Si and Zn on Al _1-Y N
technique of laminating a _Y Al _1-Y N is disclosed. According to these techniques, the emission color of the light emitting device can be made white by doping GaAl ₁ -YN with Si and Zn to form an i-type light emitting layer.

[0004]

However, as in the technique described above, a high resistance i is obtained by doping Zn, which is a p-type dopant, and Si, which is an n-type dopant.
Emitting element of the MIS structure type Ga _Y Al _1-Y N layer and the light emitting layer is luminance, luminous output both low, the practical application as a light emitting device was still insufficient.

Therefore, the present invention has been made in view of such circumstances, and an object thereof 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 the one to try.

[0006]

Among the gallium nitride-based compound semiconductors, we have focused on InGaN,
Even if Zn and Si are doped into aN, it is not a high-resistance i-type as in the past, but a low-resistance n-type having a resistivity of 10 Ω · cm or less, and a pn junction using this n-type InGaN as a light emitting layer. The above problem has been solved by realizing a light emitting device having a double hetero structure. That is, in the gallium nitride-based compound semiconductor light emitting device of the present invention, an S-type semiconductor layer is provided between the n-type gallium nitride-based compound semiconductor layer and the p-type gallium nitride-based compound semiconductor layer.
An i-type and Zn-doped n-type In _X Ga _1-X N (where X is in the range of 0 <X <1) is provided as a light emitting layer.

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 InAl.
A gallium nitride-based compound semiconductor containing gallium nitride, such as GaN, is a layer grown to show n-type characteristics by doping an n-type dopant such as Si, Ge, Se, or Te if it is n-type, If p-type, for example, Zn, Mg, C
A layer grown by doping with a p-type dopant such as d, Be, or Ca to exhibit p-type characteristics. In the case of an n-type gallium nitride-based compound semiconductor, even if it is not doped, it has a property of becoming an n-type. 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, Japanese Patent Application No. 3-35 previously filed by us has been proposed.
The annealing treatment disclosed in No. 7046 may be performed.

Also, n-type I doped with Zn and Si
The X value of n _X Ga _{1 -X} N is preferably adjusted within the range of 0 <X <0.5. By setting the X value to be greater than 0, the emission color will be 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, if the X value is 0.5 or more, it is difficult to obtain InGaN having excellent crystallinity, and it becomes difficult to obtain a light emitting element having excellent light emitting efficiency. Therefore, the X value is preferably less than 0.5.

Zn and Si in n-type InGaN
It is preferable to adjust the concentration of both to within the range of 1 × 10 ¹⁷ / cm ³ to 1 × 10 ²¹ / cm ³ . If it is less than 1 × 10 ¹⁷ / cm ^3, it is difficult to obtain a sufficient emission intensity and 1 × 10 ²¹
If it is more than / 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, n doped with 1 × 10 ¹⁸ / cm ^{3 of} Zn is shown.
-Type In0.15Ga0.85N layer and n-type In0.15G doped with Zn at 1 × 10 ¹⁹ / cm ³ and Si at 5 × 10 ¹⁹ / cm ³
The photoluminescence (PL) was measured at room temperature by irradiating the a0.85N layer with a He-Cd laser, and the emission intensities thereof are compared and shown. Note that In doped only with Zn
The spectral intensity of the GaN layer is shown by magnifying the actual intensity ten times. As shown in this figure, the PL spectrum (n) of n-type InGaN doped with only Zn and the PL spectrum (a) of n-type InGaN doped with Si and Zn all have their main emission peaks at 490 nm. However, the emission intensity of (a) is 10 times or more higher. This is the Zn-doped InGaN
By further doping Si, the donor concentration increases,
It is estimated that the emission intensity is increased by the pair emission of the donor and the acceptor. Because undoped InGa
N has an electron carrier concentration of about 1 × 1 depending on the growth conditions.
It exhibits an n-type of about 0 ¹⁷ / cm ³ to 1 × 10 ²² / cm ³ . This is because InG with a certain number of donors being undoped
It shows that it remains in aN. Therefore, when Zn is doped into this non-doped InGaN, the donor donor of the residual donor and the doped Zn acceptor
The pair emission of the 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 conditions, and it is difficult to obtain InGaN having a constant donor concentration with good reproducibility. . Therefore, the effect of Si doping is to newly dope Si to increase the donor concentration and stably obtain a constant donor concentration with good reproducibility. In fact, it was found that by doping Si, the electron carrier concentration increased from 1 × 10 ¹⁸ / cm ³ to 2 × 10 ¹⁹ / cm ³ by one digit, and the donor concentration increased. Therefore, the amount of Zn to be doped can be increased by the amount of increased donors.
It is estimated that the blue emission intensity increases as the number of acceptor pair emissions increases.

The gallium nitride-based compound semiconductor light-emitting device of the present invention has a double hetero structure having n-type InGaN doped with Si and Zn as a light-emitting layer to obtain a conventional i-type GaAlN doped with Si and Zn. The light emission efficiency and the light emission intensity can be remarkably improved as compared with the light emitting element having the MIS structure having the light emitting layer.

[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, the inside of the reaction vessel was sufficiently replaced with hydrogen, and then the temperature of the substrate was raised to 1050 ° C. while flowing hydrogen to clean the sapphire substrate. I do.

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 to 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. Si was added at 1 × 10 ²⁰ / cm ^3.
A 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 gas, and silane gas is used as the dopant gas. Using DEZ (diethyl zinc), S
An n-type In0.15Ga0.85N layer doped with i of 5 × 10 ¹⁹ / cm ³ and Zn of 1 × 10 ¹⁹ / cm ^{3 is} grown to 100 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 dopant gas
(Cyclopentadienyl magnesium) and Mg
0.8 μ of p-type GaN layer doped with 2 × 10 ²⁰ / cm ³
m to grow.

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 p
After forming ohmic electrodes on the n-type GaN layer and the n-type GaN layer and cutting into chips of 500 μm square, a light emitting diode was formed by a conventional method. The light emission output was 300 μW at 20 mA, and the luminance was 900 mcd (millicandela).
The emission wavelength was 490 nm.

[Embodiment 2] In Embodiment 1, the n-type In
Si concentration of 0.15Ga0.85N layer is 2 × 10 ²⁰ / cm ³ , Zn
A blue light emitting diode was similarly obtained except that the concentration was set to 5 × 10 ¹⁹ / cm ^3, and the emission output was 300 μW at 20 mA, the luminance was 920 mcd, and the emission wavelength was 490 nm.

[Third Embodiment] In the first embodiment, the n-type In
The Si concentration of the 0.15Ga0.85N layer is 5 × 10 ¹⁸ / cm ³ , Zn
A blue light emitting diode was similarly obtained except that the concentration was set to 1 × 10 ¹⁸ / cm ^3, and the emission output was 280 μW at 20 mA, the luminance was 850 mcd, and the emission wavelength was 490 nm.

[Embodiment 4] In Embodiment 1, the n-type In
A blue light emitting diode was obtained in the same manner except that the In molar ratio of GaN was In0.25Ga0.75N.
Luminous output power of 250 μW at mA, brightness of 1000 mc
The emission wavelength was 510 nm.

Comparative Example 1 In Example 1, Zn was not doped with Si and Zn-doped In with a Zn concentration of 1 × 10 ¹⁸ / cm ³ was used.
When a light emitting diode was made in the same manner except that 0.15 Ga0.85 N was grown, a light emission output of 180 mA was obtained at 20 mA.
Only μW, brightness 400 mcd, emission wavelength 490
was nm.

Comparative Example 2 In the step of growing the Si, Zn-doped n-type In0.15Ga0.85N layer of Example 1,
Using TMG and ammonia as a source gas, silane gas and DEZ as a dopant gas, Si is 1 × 10 ¹⁸ / cm ³ and Z.
An i-type GaN layer doped with n of 1 × 10 ²⁰ / cm ³ is grown. After the growth of the i-type GaN layer, a part of the i-type GaN layer is similarly etched to expose the n-type GaN layer, and the n-type G
An electrode is provided on the aN layer and the i-type GaN layer, and a light emitting diode having a MIS structure is used. The light emission output is 1 at 20 mA.
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 has a double hetero structure having n-type InGaN doped with Si and Zn as a light-emitting layer, and therefore has a conventional MIS structure. The luminous efficiency and the luminous intensity are significantly increased as compared with the light emitting element. 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.

[0026]

[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.

Claims (1)

[Claims] 1. An n-type gallium nitride-based compound semiconductor layer and p
N _- type In _X Ga _1-X N (where X is 0
It is a range of <X <1. ) As a light emitting layer, a gallium nitride-based compound semiconductor light emitting device.