JP2560964B2 - 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 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, 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 light emitting device having a MIS structure in which a type Ga _Y Al ₁ -YN layer is used as a light emitting layer has a low light emission output and is still insufficient for practical use as a light emitting device.

Accordingly, the present invention has been made in view of such circumstances, and an object of the present invention is to improve the light emitting output of a light emitting device by using a gallium nitride compound semiconductor having a pn junction. Is what you do.

[0006]

Among the gallium nitride-based compound semiconductors, we have focused on InGaN,
doped with p-type dopant and n-type to aN, the n-type InGaN gallium nitride compound form a light emitting layer of a semiconductor
The above problems have been solved by realizing a light emitting device . That is, while the gallium nitride-based compound semiconductor light-emitting device of the present invention the n-type gallium nitride-based compound semiconductor layer and a p-type gallium nitride-based compound semiconductor layer, n-type p-type dopant is doped In _{x Ca} 1-x N (however, X is 0 <X
It is a range of <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 InA.
For a gallium nitride-based compound semiconductor containing gallium nitride such as lGaN, if it is n-type, for example, Si, Ge, Te, Se
Is a layer grown to show n-type characteristics by being doped with an n-type dopant such as Zn, Mg, C
A layer doped with a p-type dopant such as d, Be, or Ca to grow 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. The light emission output can be further improved by lowering the resistance.

In particular, the electron carrier concentration in the n-type InGaN layer is preferably adjusted within the range of 1 × 10 ¹⁷ / cm ^{3 to} 5 × 10 ²¹ / cm ³ . Electron carrier concentration is 1
Less than × 10 ¹⁷ / cm ³ or 5 × 10 ²¹
If it is more than / cm ³ , there is a tendency that practically sufficient emission output cannot be obtained. Further, the electron carrier concentration and the resistivity are inversely proportional, and when the concentration is approximately 1 × 10 ¹⁵ / cm ³ or less, InGaN tends to be a highly resistant i-type, which makes it impossible to measure the electron carrier concentration. The electron carrier concentration can be adjusted to the above range by, for example, a method of adjusting the p-type dopant concentration in InGaN, a method of doping the n-type dopant into InGaN at the same time as the p-type dopant, or the like. P doping InGaN
The type dopant and the n-type dopant are not particularly changed, and the p-type dopant is, for example, Zn, Mg, Cd, Be, Ca, etc., as described above, and the n-type dopant is Si, Ge, Te, Se, etc. Can be used.

Further, the X value of n-type In _x Ga _1-x N is 0.
It is preferable to adjust the range of <X <0.5. By setting the X value to be greater than 0, the emission color becomes approximately 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.

[0010]

In FIG. 1, an n-type G doped with Si is first formed on the base plate.
Growing an aN layer, then n-type In0.15Ga0.85
P-type GaN with N layer grown and then Mg doped
When a layer is grown to form a light emitting device having a double hetero structure with a pn junction and emitting light as a light emitting diode, the electron carrier concentration of the n-type In0.15Ga0.85N and the relative light emission output of the light emitting diode. Shows the relationship with. The n-type In0.15Ga0.85N layer is
After growing by doping Zn as a p-type dopant, the electron carrier concentration of the layer was measured by a Hall measuring device. Each point in FIG. 1 is 1 × 10 ¹⁶ , 1 × 10 in order from the left.
¹⁷ , 4 × 10 ¹⁷ , 1 × 10 ¹⁸ , 3 × 10 ¹⁸ , 1
X10 ¹⁹ , 4x10 ¹⁹ , 1x10 ²⁰ , 3x10
²⁰ shows the electron carrier concentration of 1 × 10 ²¹ , 5 × 10 ²¹ / cm ³ .

As shown in this figure, the n-type InG of the present invention is used.
In the case of a gallium nitride compound semiconductor light emitting device using aN as a light emitting layer, the light emission output of the light emitting device changes depending on the electron carrier concentration of n-type InGaN. Light emission output is n-type InGa
The electron carrier concentration of the N layer sharply increases from around 10 ¹⁶ / cm ^3, reaches its maximum around 1 × 10 ¹⁹ / cm ³ , and tends to sharply decrease again after that.
In this figure, n-type GaN and i
The light emission output of the MIS structure light emitting device made of type GaN is
About 1/10 of the maximum light emission output of the light emitting device of the present invention
As a result of considering the practical range, the electron carrier concentration is 1 × 10 ¹⁷ / cm ^{3 to} 5 × 10 ²¹ /
A range of cm ³ is preferred. As described above, in the light emitting device of the present invention, it is presumed that the light emission output changes due to the change of the electron carrier concentration of the n-type InGaN layer which is the light emitting layer, for the following reason.

It is known that InGaN grows non-doped (without addition) and exhibits an n-type due to the formation of nitrogen vacancies. The residual electron carrier concentration of this non-doped n-type InGaN is about 1 × 10 ¹⁷ depending on the growth conditions.
/ ^Cm 3 shows the value of about to 1 × ¹⁰ 22 / cm ^3. Further, by doping this n-type InGaN layer with a p-type dopant (Zn in the case of FIG. 1) which becomes an emission center,
The electron carrier concentration in the n-type InGaN layer is reduced. Therefore, if the p-type dopant is doped so that the electron carrier concentration is extremely reduced, the n-type InGaN becomes i-type with high resistance. The emission output changes by adjusting the electron carrier concentration, suggesting the possibility of DA pair emission in which the emission center of Zn, which is a p-type dopant, forms a pair with a donor impurity to emit light. , I'm not sure about the detailed mechanism. What is important is that the intensity of the emission center is clearly increased in n-type InGaN in which both a donor impurity (for example, an n-type dopant and a non-doped InGaN) that creates a certain amount of electron carriers and a p-type dopant that is an acceptor impurity are present. That is.

As described above, p is added to the undoped n-type InGaN layer.
Although the method of doping the type dopant to change the electron carrier concentration has been described, another donor impurity that creates electron carriers in the n-type InGaN layer, that is, the n-type dopant, is added to the p-type dopant.
The n-type InGaN layer may be doped simultaneously with the type dopant.

[0014]

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.

Subsequently, the temperature is lowered to 510 ° C., and hydrogen is used as a carrier gas, and ammonia and TMG are used as source gases.
(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 increased to 1030 ° C. When the temperature reached 1030 ° C, n-type G doped with Si using TMG and ammonia gas as the source gas and silane gas as the dopant gas.
The aN layer is grown to 4 μm.

After the growth of the n-type GaN layer, the raw material gas and the dopant gas are stopped, the temperature is set to 800 ° C., nitrogen is used as the carrier gas, and TMG, TM1 (trimethylindium), ammonia and the dopant gas are used as the original gases. DEZ (diethyl zinc) is used as the n-type In0.15Ga0.85N layer doped with Zn to grow 100 angstroms. In addition, this n-type In0.15 Ga
The electron carrier concentration of the 0.85N layer is 1 × 10 ¹⁹ / cm
It was ³ .

Next, the source gas and the dopant gas are stopped,
The temperature is again raised to 1020 ° C. and T
MG and ammonia, Cp2Mg as a dopant gas
(Cyclopentadienyl magnesium) and Mg
Is grown to a thickness of 0.8 μm.

After the growth of the p-type GaN layer, the substrate is taken out of the reaction vessel, and the substrate is placed in a nitrogen atmosphere by an annealing apparatus.
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 obtained as described above 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, it was 300 μW and the emission wavelength was 490 nm.

Example 2 In Example 1, except that the gas flow rate of DEZ is adjusted to grow the n-type In0.15Ga0.85N layer so that the electron carrier concentration is 4 × 10 ¹⁷ / cm ^3. When a blue light emitting diode was obtained in the same manner, the emission output was 30 μW and the emission wavelength was 490 nm at 20 mA.

Example 3 In Example 1, when the n-type In0.15Ga0.85N layer was grown, the electron carrier concentration was 1 × 10 ²¹ / cm 3.
^A blue light emitting diode was obtained in the same manner except that the light emission output was 30 μW and the emission wavelength was 4 at 20 mA.
It was 90 nm.

Example 4 In Example 1, when the n-type In0.15Ga0.85N layer was grown, the electron carrier concentration was 1 × 10 ¹⁷ / cm 3.
^A blue light emitting diode was obtained in the same manner except that the light emitting output was 5 μW at 20 mA and an emission wavelength of 49
It was 0 nm.

[Example 5] The n-type In0.15Ga0.85N layer in Example 1
When growing, the electron carrier concentration is 5 × 10 ²¹ / cm
^A blue light emitting diode was obtained in the same manner except that the light emitting output was 3 μW and the emission wavelength was 49 nm at 20 mA.
It was 0 nm.

Example 6 In Example 1, when growing an n-type In0.15Ga0.85N layer, silane gas was newly added as a dopant gas and Zn and Si were doped to obtain an electron carrier concentration of 1 × 10. except that the ¹⁹ / cm ^3, was obtained a blue light-emitting diodes in the same manner, the light emission output at 20 mA 300 [mu] W, and a light-emitting wavelength 490 nm.

Comparative Example 1 Zn-doped n-type In0.15Ga0.85N of Example 1
In the step of growing the layer, a high resistance i-type GaN layer doped with Zn is grown by using TMG, ammonia as a source gas and DEZ as a dopant gas. i-type GaN
After the layer growth, a portion of the i-type GaN layer is similarly etched to expose the n-type GaN layer, and the n-type GaN layer and the i-type Ga are exposed.
When an electrode was provided on the N layer to form a MIS structure light emitting diode, the light emission output was 1 μW at 20 mA and the brightness was only 2 mcd.

[0028]

The gallium nitride-based compound semiconductor light-emitting device of the present invention comprises a p-type gallium nitride-based compound semiconductor layer and an n-type nitride-based compound semiconductor layer.
A p-type dopant is provided between the gallium nitride-based compound semiconductor layers.
Unique to disposing doped n-type InGaN as a light emitting layer
Due to the configuration, compared with the conventional MIS structure light emitting device,
Luminous efficiency and luminous intensity are significantly increased. In addition, n-type In
By setting the electron carrier concentration in the GaN layer to an optimum value, it is possible to achieve a light emission output and light emission brightness that are 100 times or more as compared with a conventional light emitting element .

[Brief description of drawings]

FIG. 1 shows an n-type In of a light emitting device according to an embodiment of the present invention.
The figure which shows the relationship between the electron carrier concentration of a GaN layer, and relative light emission output.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References 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-A-4-236477 (JP, A) JP-A-4-236478 (JP, A) JP-A-4-199752 (JP, A)

Claims (2)

(57) [Claims] 1. An n-type gallium nitride-based compound semiconductor layer,
Between the p-type gallium nitride-based compound semiconductor layer, p-type dopant is n-type doped In x _Ga 1-x _N layer (where, X is in the range 0 <X <1 in.) as a light-emitting layer A gallium nitride-based compound semiconductor light emitting device. 2. The electron carrier concentration of the n-type In _x Ga _1-x N layer is 1 × 10 ¹⁷ / cm ^{3 to} 5 × 10 ²¹ / c.
The gallium nitride-based compound semiconductor light emitting device according to claim 1, wherein the gallium nitride-based compound semiconductor light emitting device is in the range of m ³ .