JPH06209122A - Indium gallium nitride semiconductor and growing method thereof - Google Patents

Abstract

PURPOSE:To provide InGaN having high quality and excellent crystallizability and a growing method thereof in excellent reproducibility. CONSTITUTION:This indium gallium semiconductor represented by a general formula of InalphaGal-alphaN (where 0<alpha<0.5) is grown by an organic metal vapor deposition process meeting the requirement assuming the growing temperature ( deg.C) (a) to be on X axis and the growing rate (Angstrom /min) (b) to be on Y axis within the region encircled by respective coordinates of a (659, 1), b (650, 5), c (900, 60), d (900, 1) in the annexed figure.

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 blue light emitting diodes, blue laser diodes 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) and gallium nitride-based compound semiconductors such as gallium aluminum nitride (GaAlN) have attracted attention. Among them, InGaN has a bandgap of 2 eV to 3.4 eV and thus is regarded as very promising.

Conventionally, metal organic chemical vapor deposition method {hereinafter, MOC
It is called a VD (Metal Organic Chemical Vapor Deposition) method. }, The InGaN was grown on the sapphire substrate at a low growth temperature of 500 ° C to 600 ° C. Because the melting point of InN is about 500
℃, the melting point of GaN is about 1000 ℃, 60
When InGaN is grown at a high temperature of 0 ° C. or higher, InGa
The decomposition pressure of InN in N becomes about 10 atm or more, and I
This is because most of the nGaN is decomposed and only the deposits of Ga metal and In metal are formed. Therefore, in order to grow InGaN conventionally, the growth temperature had to be kept low.

InGa grown under such conditions
The crystallinity of N is very poor. For example, even when photoluminescence measurement is performed at room temperature, almost no interband emission is observed, only a slight emission from a deep level is observed, and blue emission is observed. It never happened. Moreover, X
Even if an InGaN peak was detected by line diffraction, almost no peak was detected, and the crystallinity was closer to that of 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, In having high quality and excellent crystallinity is used.
Realization of GaN is strongly desired. However, InG
There have been no reports of successful growth of aN,
The reality 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 having high quality and excellent crystallinity, and to obtain the crystal reliably and with good reproducibility. It provides a method to be performed.

[0006]

[Means for Solving the Problems]
As a result of repeated experiments on the growth by the OCVD method, it was newly found that the crystallinity of GaN was remarkably improved by growing it on GaN at a growth temperature and a growth rate within a specific range. The present invention has been accomplished.

In other words, the growth method of the present invention is based on the general formula InαGa1-αN (where α is 0 <α <
It is in the range of 0.5. ) Is a method of growing an indium gallium nitride semiconductor represented by
Is the X-axis and the growth rate (angstrom / min) is the Y-axis, and a (650,1), b (650,5), and
It is characterized in that it is grown on gallium nitride under the condition of the region surrounded by the coordinates of c (900, 60) and d (900, 1).

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

The growth temperature must be adjusted within the range of 650 ° C to 900 ° C. InGa even at a temperature lower than 650 ° C
It is possible to grow N, but as described above, 6
If the temperature is not higher than 00 ° C., it is difficult for GaN crystals to grow, and thus it is difficult to form InGaN crystals, and even if they are formed, InGaN having poor crystallinity as in the conventional case is obtained. Again 600
InGaN with excellent reproducibility and excellent crystallinity at ℃ to 650 ℃
Tends to be difficult to obtain. InGa is easily decomposed at a temperature higher than 900 ° C., so InGa
N tends to be GaN. Growth temperature is 700
Most preferred is the range of ° C to 850 ° C.

Although there are Si, SiC and the like for the substrate, sapphire is often used. Further, by forming a buffer layer made of GaXAl1-XN (0≤X≤1) on the substrate at a low temperature, the crystallinity of GaN grown on the substrate can be improved. Ga
The N buffer layer can improve the crystallinity of the GaN layer grown thereon.

The molar ratio of indium of the source gas of indium in the source gas supplied during growth is 1 gallium:
It is desirable to adjust to 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. This is because at a growth temperature of 650 ° C. or higher, InN is decomposed to some extent and
It becomes difficult to enter the aN crystal. Therefore, it is preferable to supply more indium than the decomposed portion,
More nN can be included in the GaN crystal.

As described above, InN is very easily decomposed at 650 ° C. or higher, and GaN is hard to be decomposed. Therefore, the growth rate of InGaN is controlled 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
To increase n, the growth should be carried out at a low temperature of around 650 ° C., or the molar ratio of In in the source gas should be increased, while to increase Ga, the growth should be carried out at a high temperature of around 900 ° C. Good. It is preferable that the molar ratio of indium gas be increased as the temperature grows, for example, 90
At a growth temperature around 0 ° C., indium is converted into gallium 10
By supplying approximately 50 times, InαGa1-αN having an α value of less than 0.5 can be obtained.

Furthermore, InαGa1-αN having excellent crystallinity
The α value for which is obtained 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 the yellow region and it cannot be used as blue. The reason for limitation is less than 5.

Furthermore, by using nitrogen as a carrier gas for these source gases, it is possible to obtain In
InN in GaN can be prevented from decomposing and coming out of the crystal lattice.

[0016]

In the past, an InGaN layer was grown on a sapphire substrate, but since the lattice constant mismatch between sapphire and InGaN is about 15% or more, it is considered that the crystallinity of the obtained crystal deteriorates. 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 this GaN layer may be replaced with Al, and n-type impurities such as Si and Ge, Zn and M may be substituted.
It may be doped with p-type impurities such as g and Cd, which is within the technical range.

In FIG. 1, a GaN buffer layer and a GaN layer are sequentially stacked on a sapphire substrate by the MOCVD method, and then an InGaN layer is grown on the GaN layer at various growth temperatures and growth rates. The resulting InGaN layer was irradiated with a He—Cd laser at room temperature, and its photoluminescence measurement was performed. As a result, I as shown in FIG.
It is the figure which plotted only what obtained the light emission peak between bands of nGaN. At the same time, the ranges of the growth temperature and the growth rate of claim 1 of the present application are also shown. Note that, as shown in FIG. 2- (A), a material in which sharp InGaN band emission is obtained can be considered to have excellent InGaN crystallinity.

FIG. 2 shows the growth temperature 805 on the GaN layer.
In 0.15 Ga 0.86 N at a growth rate of 20 Å / min (A) and a growth rate of 6
It is a figure which compares and shows the spectrum of the photoluminescence measurement with what was grown at 0 angstrom / min (B). In this figure, the emission intensity on the vertical axis is an arbitrary unit, and the emission intensity of the spectrum of (B) is shown by enlarging the measured value by 6 times. That is, 1 / of the emission intensity of (B)
6 is the same as the scale on the vertical axis in (A).

As shown in this figure, (A) is 406 nm.
Intense band-to-band emission of In0.15Ga0.86N is observed in the vicinity, whereas in (B), the intensity is weak and the emission from a deep level is strong. That is, (A) is (B)
It shows that the crystallinity is overwhelmingly superior to
Looking at the peak around 6 nm, (A) has an emission intensity that is about 35 times greater than that of (B).

Thus, in the range shown in FIG. 1, that is, the growth temperature at point a is 650 ° C., the growth rate is 1 Å / min, the growth temperature at point b is 650 ° C., the growth rate is 5 Å / min, and the growth temperature at point c. At a temperature within the range of 900 ° C., a growth rate of 60 Å / min, a growth temperature of 900 ° C. at the point d, and a growth rate of 1 Å / min,
Excellent crystallinity can be achieved by growing InGaN on GaN. Furthermore, it is possible to recommend a range surrounded by a growth temperature of 700 to 850 ° C. with a large number of plots as a preferable range.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The growth method of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 3 shows the MOC used in the growth method of the present invention.
FIG. 3 is a schematic cross-sectional view showing the configuration of the main part of the VD device, showing the structure of a reaction part and a gas system diagram communicating with the reaction part. Reference numeral 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 shaft for rotating and vertically moving the susceptor, and 5 is a diagonal to the substrate. , Or a quartz nozzle that supplies the raw material gas horizontally, and 6 is a conical device that presses the raw material gas against the substrate surface by supplying the inert gas vertically toward the substrate to bring the raw material gas into contact with the substrate. A quartz tube, 7 is a substrate. TMG, T
The organometallic compound source such as MI is vaporized by a small amount of bubbling gas and supplied into the reaction vessel by the carrier gas which is the main gas. Although not shown in particular, the flow rates of the source gases and the 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 the susceptor 2, and the inside of the reaction vessel is sufficiently replaced with hydrogen.

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

Then, the temperature was lowered to 510 ° C., and the quartz nozzle 5 was used to feed ammonia (NH ₃ ) 4 liter / min.
Hold MG for 1 minute while flowing MG at 27 × 10 ⁻⁶ mol / min and hydrogen as carrier gas at 2 liter / min.
The aN buffer layer is grown to about 200 Å. During this time, hydrogen is supplied from the conical quartz tube 7 to 10
Continue to flow liters / minute and nitrogen at 10 liters / minute and slowly rotate susceptor 2.

After the growth of the buffer layer, only TMG is stopped and the temperature is raised to 1020 ° C. When the temperature reaches 1020 ℃, hydrogen is also used as carrier gas and TMG is added to 60
Flowing at 10 ⁻⁶ mol / min for 30 minutes to grow the GaN layer to about 2 μm.

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

After the growth, the wafer was taken out from the reaction container, the InGaN layer was irradiated with 10 mW of He—Cd laser, and the photoluminescence measurement was performed at room temperature. Indicated.

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

[Comparative Example] When InGaN is grown after the growth of the GaN layer, the flow rate of TMG is tripled and Si-doped I
InGaN is grown in the same manner as in Example 1 except that nGaN is grown for 20 minutes at a growth temperature of 805 ° C. and a growth rate of 60 Å / min. When the photoluminescence measurement of this InGaN was performed, a weak interband emission was shown at around 430 nm, and a deep level broad emission near 550 nm was dominant. It was found that the crystallinity of InGaN grown from this is very poor.

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

[0031]

In the past, the only semiconductor material that has been put to practical use in light emitting diodes whose emission wavelength is in the blue region is SiC, and other materials have not yet reached the practical range. Also, a blue laser diode that emits light at room temperature has not been reported yet.

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

[Brief description of 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 obtained by photoluminescence measurement of InGaN according to an embodiment of the present invention and InGaN according to an embodiment outside the scope of the present invention.

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

[Explanation of symbols]

1 ... Reaction container 2 ... Susceptor 3 ... Heater 4 ... Control shaft 5 ...・ Quartz nozzle 6 ・ ・ ・ ・ ・ ・ ・ ・ Conical quartz tube 7 ・ ・ ・ ・ ・ ・ Substrate

Claims (2)

[Claims] 1. The general formula In is obtained by a metal organic chemical vapor deposition method.
A method for growing an indium gallium nitride semiconductor represented by αGa1-αN (where α is in the range of 0 <α <0.5), wherein the growth temperature (° C) is the X axis, the growth rate (angstrom is / Min) as the Y axis
(650,1), b (650,5), c (900,6)
0) and d (900, 1) are grown on gallium nitride under the conditions in the region surrounded by the coordinates, and a method for growing an indium gallium nitride semiconductor is provided. 2. The method for growing an indium gallium nitride semiconductor according to claim 1, wherein the gallium nitride is gallium aluminum nitride in which a part of the gallium is replaced with aluminum.