JP2751987B2 - Method for growing indium gallium nitride semiconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing an indium gallium nitride semiconductor used for a blue light emitting diode, a blue laser diode and the like.

[0002]

2. Description of the Related Art Gallium nitride (GaN) and indium gallium nitride (InGa) are practical semiconductor materials used for blue diodes, blue laser diodes, and the like.
N), gallium nitride-based compound semiconductors such as gallium aluminum nitride (GaAlN) have been attracting attention, and among them, InGaN is very promising because it has a band gap of 2 eV to 3.4 eV.

Conventionally, metal organic chemical vapor deposition (hereinafter referred to as MOC)
It is called VD (Metal Organic Chemical Vapor Deposition) method. When InGaN is grown by｝, it was grown on a sapphire substrate at a low growth temperature of 500 ° C. to 600 ° C. Because the melting point of InN is about 500
° C, and the melting point of GaN is about 1000 ° C.
When InGaN is grown at a high temperature of 0 ° C. or more, InGa
When the decomposition pressure of InN in N becomes about 10 atm or more,
This is because nGaN is almost completely decomposed and only Ga metal and In metal deposits are formed. Therefore, conventionally, when growing InGaN, the growth temperature had to be maintained at a low temperature.

InGaP grown under such conditions
The crystallinity of N is very poor. For example, even if photoluminescence measurement is performed at room temperature, emission between bands is hardly observed, emission from a deep level is only slightly observed, and blue emission is observed. I never did. And X
Even if an attempt was made to detect the peak of InGaN by line diffraction, almost no peak was detected, and the crystallinity was closer to an amorphous crystal rather than a single crystal.

[0005]

A blue light emitting diode,
In order to realize a blue light emitting device such as a blue laser diode, it is necessary to use high quality and excellent crystallinity.
Realization of GaN is strongly desired. However InG
There have been no reports of the successful growth of aN,
The fact is that the growth method is not well known. Therefore, the present invention has been made to solve this problem, and an object of the present invention is to provide a method for growing InGaN with high quality and excellent crystallinity, and to obtain the crystal with good reproducibility. It provides a method to be used.

[0006]

Means for Solving the Problems We have developed InGaN into M
As a result of repeating a number of experiments in growing by the OCVD method, it has been newly found that the crystallinity is significantly improved by growing on GaN at a growth temperature and a growth rate within a specific range. The present invention has been accomplished.

[0007] In other words, the growth method of the present invention, a raw material gas
Gallium source gas, indium source gas, and nitrogen
Using the source gas and the MOCVD method, the general formula Inα
A method of growing an indium gallium nitride semiconductor represented by Ga1-αN (where 0 <α <0.5), wherein a growth temperature (° C.) is an X-axis, a growth temperature (angstrom /
A) (650, 1) and b in FIG.
(650,5), c (900,60), d (900,1)
Nitrogen under the conditions of the area surrounded by the coordinates, which then grow
Gallium nitride layer or gallium aluminum nitride layer
Through the buffer layer grown at low temperature, from the buffer layer
Gallium nitride layer or gallium nitride layer grown at high temperature
It is characterized by being grown on a aluminum layer .

In the growth method of the present invention, as a source gas used for the MOCVD method, for example, a gallium source is trimethylgallium (TMG) or triethylgallium (TEG).
G), trimethylindium (TM) as an indium source
I), an organometallic compound gas such as triethylindium (TEI), and a gas such as ammonia (NH ₃ ) or hydrazine (N ₂ H ₄ ) can be preferably used as a nitrogen source. These gases are mixed with a carrier gas. Then, InGaN can be grown by spraying the heated substrate. The growth rate of InGaN can be adjusted by controlling the gas flow rate of the Ga source.

[0009] The growth temperature must be adjusted in the range of 650 ° C to 900 ° C. InGa even at temperatures lower than 650 ° C
Although it is possible to grow N, as described above, 6
When the temperature is lower than 00 ° C., GaN crystals are difficult to grow, so that it is difficult to form InGaN crystals. Also 600
InGaN with excellent reproducibility and excellent crystallinity at ℃ to 650 ℃
Tends to be difficult to obtain. If the temperature is higher than 900 ° C., InN is easily decomposed, so that InGa
N tends to be GaN. The growth temperature is 700
Most preferably, it is in the range of 850C to 850C.

Although there are Si, SiC and the like for the substrate, sapphire is often used. Further, by forming a buffer layer made of Ga _x Al ₁ -xN (0 ≦ x ≦ 1) on the substrate at a low temperature, the crystallinity of GaN grown on the buffer layer can be improved. Ga rather than AlN
The N buffer layer can improve the crystallinity of the GaN layer grown thereon.

The molar ratio of indium in the gas of the indium source in the source gas supplied during growth is 1 gallium to 1 gallium.
It is desirable to adjust it to preferably 0.1 or more, more preferably 1.0 or more. If the molar ratio of indium is less than 0.1, it is difficult to obtain a mixed crystal of InGaN, and the crystallinity tends to deteriorate. At a growth temperature of 650 ° C. or higher, the decomposition of InN occurs to some extent, and
It becomes difficult to enter the aN crystal. Therefore, by supplying a larger amount of indium than the decomposition component, I
More nN can be included in the GaN crystal.

At 650 ° C. or higher, InN is very easily decomposed and GaN is hardly decomposed, so that the growth rate of InGaN is governed by the growth rate of GaN. That is, the growth rate can be freely adjusted by adjusting the gas flow rate of the gallium source as described above.

The desired α value of InαGa1-αN can be appropriately changed by changing the molar ratio of indium gas to gallium and the growth temperature. For example I
In order to increase n, it is necessary to grow at a low temperature of about 650 ° C., or to increase the molar ratio of In in the source gas, while to increase Ga, it is necessary to grow at a high temperature of about 900 ° C. Good. It is preferable that the molar ratio of indium gas be increased as the temperature grows at a high temperature.
At a growth temperature of around 0 ° C., indium is converted to 10 g of gallium.
By supplying about 50 times, it is possible to obtain InαGa ₁ -αN having an α value of less than 0.5.

Further, InαGa1-αN having excellent crystallinity
Is in the range of 0 <X <0.5, and α
When InαGa1-αN having a value of 0.5 or more is used as a light-emitting element of a light-emitting device such as a light-emitting diode, the emission wavelength is in a yellow region and cannot be used as blue, so the α value is 0.1. Less than 5 was the limiting reason.

Further, by preferably using nitrogen as a carrier gas for these source gases, In
It is possible to prevent InN in GaN from decomposing and coming out of the crystal lattice.

[0016]

In the past, an InGaN layer was grown on a sapphire substrate. However, since the lattice constant of sapphire and InGaN is about 15% or more, the crystallinity of the obtained crystal is considered to be deteriorated. On the other hand, in the present invention, G
By growing on the aN layer, the lattice constant irregularity can be reduced to 5% or less, so that InGaN having excellent crystallinity can be formed. In the growth method of the present invention, part of Ga in the GaN layer may be replaced with Al, and n-type impurities such as Si and Ge, Zn, M
A p-type impurity such as g or Cd may be doped, which is within the technical range.

FIG. 1 shows that a GaN buffer layer and a GaN layer are sequentially stacked on a sapphire substrate by MOCVD, and then an InGaN layer is grown on the GaN layer at various growth temperatures and growth rates. A He-Cd laser was irradiated to the InGaN layer at room temperature, and the photoluminescence was measured. As a result, as shown in FIG.
FIG. 9 is a diagram in which only emission peaks between nGaN bands are obtained. In addition, the ranges of the growth temperature and the growth rate according to claim 1 of the present application are also shown. Note that, as shown in FIG. 2A, those in which sharp interband emission of InGaN is obtained can be regarded as having excellent crystallinity of InGaN.

FIG. 2 shows that the growth temperature 805
In ° C., which was grown at a growth rate of 20 Å / min In0.15Ga0.8 5 N and (A), the growth rate 6
It is a figure which shows and compares the spectrum of the photoluminescence measurement with the thing (B) grown at 0 angstrom / min. In this figure, the luminous intensity on the vertical axis is an arbitrary unit, and the luminous intensity of the spectrum in FIG. That is, 1 / l of the emission intensity of (B)
6 is the same as the scale on the vertical axis of (A).

As shown in this figure, in FIG.
For In0.15Ga0.8 5 of band-to-band emission of N is seen strong in the vicinity, has become a strong light emission from the (B) in strength is weak, yet a deep level. That is, (A) is (B)
Shows that the crystallinity is overwhelmingly superior to that of
Looking at the peak near 6 nm, the emission intensity of (A) is about 35 times larger than that of (B).

As described above, the range shown in FIG. 1, ie, the growth temperature at point a 650 ° C. and the growth rate of 1 Å / min, the growth temperature at point b 650 ° C., the growth rate 5 Å / min, and the growth temperature at point c Under conditions within a range between 900 ° C. and a growth rate of 60 Å / min, and a growth temperature of 900 ° C. and a growth rate of 1 Å / min at point d,
By growing InGaN on GaN, excellent crystallinity can be realized. Further, as a preferable range, a range surrounded by a growth temperature of 700 to 850 ° C. with a large number of plots can be recommended.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The growth method of the present invention will be described below in detail with reference to the drawings. FIG. 3 shows the MOC used in the growth method of the present invention.
FIG. 2 is a schematic cross-sectional view illustrating a configuration of a main part of the VD apparatus, illustrating a structure of a reaction unit and a gas system diagram communicating with the reaction unit. 1 is a reaction vessel connected to a vacuum pump and an exhaust device, 2 is a susceptor for mounting a substrate, 3 is a heater for heating the susceptor, 4 is a control axis for rotating and moving the susceptor up and down, and 5 is a diagonal toward the substrate. Or a quartz nozzle for supplying the raw material gas horizontally, and a conical nozzle 6 for supplying the raw material gas to the substrate surface by pressing the raw material gas against the substrate surface by supplying an inert gas vertically toward the substrate. A quartz tube 7 is a substrate. TMG, T
An organic metal compound source such as MI is vaporized by a slight amount of bubbling gas and supplied into the reaction vessel by a carrier gas as a main gas. Although not particularly shown, the flow rates of each source gas and carrier gas are controlled by a mass flow controller (MFC) installed in each gas line.

[Example 1] First, a well-cleaned sapphire substrate 7 is set on a susceptor 2, and the inside of a reaction vessel is sufficiently replaced with hydrogen.

Next, the temperature is raised to 1050 ° C. by the heater 3 while flowing hydrogen from the quartz nozzle 5 and held for 20 minutes to clean the sapphire substrate 7.

Subsequently, the temperature is lowered to 510 ° C., and ammonia (NH ₃ ) 4 L / min.
While holding the MG at 27 × 10 ⁻⁶ mol / min and the hydrogen as a carrier gas at 2 liter / min, hold for 1 minute and
The aN buffer layer is grown for about 200 angstroms. During this time, 10 hydrogen was supplied from the conical quartz tube 7.
The susceptor 2 is rotated slowly, with the flow of liters / minute and nitrogen flowing at 10 liters / minute.

After the growth of the buffer layer, only TMG is stopped, and the temperature is increased to 1020 ° C. When the temperature reaches 1020 ° C., hydrogen is also used as a carrier gas and TMG is
It is grown at a flow ^{rate of} × 10 ^-6 mol / min for 30 minutes to grow a GaN layer of about 2 μm.

After growing the GaN layer, the temperature is raised to 805 ° C.
Switch the carrier gas to nitrogen and use 2 liters of nitrogen /
Min, TMG 2 × 10 ^-6 mol / min, TMI 20 × 10
^-6 mol / min, 4 l / min of ammonia, and 1 × 10 ⁻⁹ mol / min of silane (SiH ₄ ) as an n-type impurity gas, while growing Si-doped InGaN at a growth rate of 2 × 10 ⁻⁹ mol / min.
Grow at 0 Angstrom / min for 60 minutes. During this time, the gas supplied from the conical quartz tube 7 is only nitrogen, and the gas is kept flowing at 20 liter / min.

After the growth, the wafer was taken out of the reaction vessel, and the InGaN layer was irradiated with a 10 mW He-Cd laser to perform photoluminescence measurement at room temperature. Indicated.

Example 2 After growing the buffer layer of Example 1, only TMG was stopped and the temperature was raised to 1020 ° C. When the temperature reaches 1020 ° C, hydrogen is used as a carrier gas and TMG is added to 54 ×
10 ^-6 mol / min, by flowing TMA at 6 × 10 ^-6 mol / min was grown for 30 minutes, Si-doped InGaN other to 2μm grow Ga0.9Al0.1N layer in the same manner as in Example 1
Is grown on the Ga0.9Al0.1N layer. After the growth, a photoluminescence measurement of the obtained InGaN layer showed that the peak wavelength of In0.15Ga0.85N was 406 nm.
Strong in-band emission.

COMPARATIVE EXAMPLE When growing InGaN after growing the GaN layer, the flow rate of TMG was tripled, and Si-doped InGaN was grown at a growth temperature of 80.
InGaN is grown in the same manner as in Example 1 except that growth is performed at 5 ° C. and a growth rate of 60 Å / min for 20 minutes. When the photoluminescence of InGaN was measured, weak interband light emission was observed at about 430 nm, and broad light emission at a deep level near 550 nm was dominant. It was found that the crystallinity of the grown InGaN was very poor.

To confirm this, the grown InG
When the X-ray rocking curve of aN was measured, it was found that the half value width was about 1 degree, the peak position was at GaN, and the crystal of InGaN was amorphous.

[0031]

Conventionally, the only semiconductor material practically used in light emitting diodes having an emission wavelength in the blue region is SiC, and other materials have not yet reached the practical range. A blue laser diode emitting at room temperature has not yet been reported.

However, according to the growth method of the present invention, I having excellent crystallinity satisfying the general formula α of 0 <α <0.5.
nαGa1-αN can be surely grown, and InGaN having α in the above range has an emission wavelength in the blue to green region. Therefore, by using the method of the present invention, a semiconductor device using a gallium nitride-based compound semiconductor can have a double hetero structure, and a blue light-emitting diode or a blue laser diode with high luminous efficiency can be realized. The utility value is very large.

[Brief description of the drawings]

FIG. 1 is a diagram showing a range of a growth temperature and a growth rate according to claim 1 of the present invention.

FIG. 2 is a diagram showing a comparison of spectra of photoluminescence measurements of InGaN according to an embodiment of the present invention and InGaN outside the scope of the present invention.

FIG. 3 is a schematic sectional view showing a configuration of a main part of an MOCVD apparatus used in one embodiment of the present invention.

[Explanation of symbols]

1 ······ Reaction vessel 2 ······························ Heater 4 ··············・ Quartz nozzle 6 ・ ・ ・ ・ ・ ・ ・ ・ Conical quartz tube 7 ・ ・ ・ ・ ・ ・ ・ ・ ・ Substrate

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 33/00 H01S 3/18 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A gas of a gallium source as a source gas;
Using a gas of an indium source and a gas of a nitrogen source , a general formula InαGa1-αN (however,
0 <α <0.5), wherein the growth temperature (° C.) is X
Axis, growth temperature (angstrom / min) as Y axis,
A (650, 1), b (650, 5), c (9)
Gallium nitride layer or nitride layer to be grown next under the conditions in the area surrounded by the coordinates of (00, 60) and d (900, 1).
Buffer grown at lower temperature than gallium aluminum layer
Through the buffer layer, the nitride grown at a higher temperature than the buffer layer.
Above gallium nitride layer or gallium aluminum nitride layer
The method of growing indium gallium nitride semiconductor, characterized in that growing.