JPH0716078B2 - Ga (0.5) In (0.5) P crystal growth method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor crystal.

(Prior Art) Ga _0.5 In _0.5 P lattice-matched to a GaAs substrate is a basic crystal of the AlGaInP system, which is a promising material for visible light semiconductor lasers, and serves as an active layer of a semiconductor laser. Therefore, it is important to control the energy gap in determining the oscillation wavelength of the laser.

The energy gap of conventional Ga _x In _1-x P (0x1) is I
It is determined by the ratio x of Ga and In of the II group element, and Ga
The energy gap of the Ga _0.5 In _0.5 P crystal lattice-matched to the As substrate was 1.90 eV.

(Problems to be solved by the invention) When changing the oscillation wavelength of a semiconductor laser, Ga _x In
_1-x and P varying the Ga composition ratio x was varied the energy gap of Ga _x an In _1-x P.

However, the lattice constant of Ga _x In _1-x P changes as the Ga composition ratio x changes, and a lattice shift occurs between the GaAs substrate and Ga _x In _1-x P. When a semiconductor crystal having such a lattice shift is made into a laser element, the reliability of the laser element is remarkably lowered.

However, until now, while keeping lattice matching with the GaAs substrate, Ga and In
No method has been provided for changing the energy gap of the Ga _x In _1-x P crystal while keeping the solid-phase composition ratio of the crystal constant.

The object of the present invention is to solve the above-mentioned problems and to reduce the Ga composition ratio to 0.5.
Another object of the present invention is to provide a method for controlling the energy gap, which changes the energy gap of a Ga _0.5 In _0.5 P crystal fixed at.

(Means for Solving Problems) In the present invention, Ga _0.5 In _0.5 P lattice-matched to the GaAs substrate
Crystals were grown by the MOCVD method, and by changing the combination of the temperature at the time of the crystal growth and the net gas flow ratio of group V to group III of the source gas, the crystallinity was not impaired and lattice matching was performed with the GaAs substrate. Until now, we will show how to control the energy gap of Ga _0.5 In _0.5 P crystal by changing the energy gap of Ga _0.5 In _0.5 P from 1.9 eV to 1.85 eV.

(Function) The energy gap of Ga _0.5 In _0.5 P on GaAs grown by the MOCVD method can be controlled as follows.

Trimethylindium or triethylindium is used as a raw material of group III In for growth of Ga _0.5 In _0.5 P crystal, and trimethylgallium or triethylgallium is used as a raw material of Ga, and the raw material gases of In and Ga are fixed at fixed values. By using phosphine (PH ₃ ) as the V group raw material and changing the flow rate of PH ₃ (V group flow rate) / (III group flow rate)
Of the growth temperature from 550 ℃
Change to 800 ℃. Here, the group III flow rate is the sum of the net flow rates of the source gases of Ga and In.

The figure shows the relationship between growth temperature, V / III ratio, and energy gap at this time. Growth temperature on X axis, V / III on Y axis
The ratio, Z axis shows the energy gap.

Energy gap of Ga _0.5 In _0.5 P lattice-matched to a GaAs substrate was continuously changed from 1.84 eV to 1.91 eV in the growth temperature range of 600 ℃ to 750 ℃ and V / III ratio of 60 to 450. , V / III ratio 410, growth temperature 650
Draw a parabolic surface with a bottom of 1.84 eV at ~ 700 ° C.

As described above, by combining the growth temperature of Ga _0.5 In _0.5 P on GaAs by the MOCVD method and the V / III ratio, Ga _0.5 In _0.5 P
The energy gap obtained by the photoluminescence measurement of can be controlled.

Note that the above curved surface is the energy gap of Ga _0.5 In _0.5 P and the growth temperature and V / I, where z is the energy gap determined by photoluminescence measurement, and z is the growth temperature and y is V / III.
The relationship of II is that (x, y, z) points are (700,60,1.895), (70
0,230,1.86), (700,410,1.85), (750,230,1.89)
5), (650,230,1.86), (600,230,1.865).

It is expressed by the formula. Where x ₁ , y ₁ , z ₁ , a, b, c are the above 6
It is a constant obtained from the point. The units of x and z are ° C and eV, respectively.

The reason why the energy gap of Ga _0.5 In _0.5 P can be changed without changing the composition ratio will be described.

The average diffusion length of group III atoms Ca and In on the Ga _0.5 In _0.5 P crystal growth surface changes depending on the growth temperature and the V / III ratio during MOVPE growth or the flow rate of PH ₃ of the group V source gas. That is, the growth mechanism changes. Also, Ga _0.5 In _0.5 P
In crystals, the arrangement state of Ga and In in the crystal has a strong correlation with the growth temperature.

Due to the above factors, the arrangement state of Ga and In on the group III sublattice of the Ga _0.5 In _0.5 P crystal, that is, the arrangement disorder, changes depending on the growth temperature or the V / III ratio during MOVPE growth. Where Ga
The Ga and In array states of Ga _0.5 In _0.5 P lattice-matched to the As substrate and the energy gap Eg have a unique correspondence. The Eg of a crystal with a disordered arrangement of Ga and In on the group III sublattice is 1.9 eV, and the Eg of a crystal with a superlattice structure of Ga and In is 1.9 eV.
It changes corresponding to the superlattice structure in the crystal up to 1.8 eV.
For example, Eg = 1.85eV grown on a (001) plane GaAs substrate.
The Ga _0.5 In _0.5 P crystal with has a Ga plane of (11) and (1
1) It has a superlattice structure with In planes arranged alternately. By having such a superlattice structure, the energy band structure of the crystal changes compared with a crystal having a disordered arrangement of Ga and In, and the energy gap of the Ga _0.5 In _0.5 P crystal becomes smaller. As mentioned above, the energy gap
It can be changed while keeping the Ga composition ratio constant.

(Example) Hereinafter, an example in which the energy gap is changed without changing the composition ratio of Ga and In of the Ga _0.5 In _0.5 P crystal on GaAs grown by the MOCVD method will be shown.

Trimethylindium and triethylgallium were used as Group III raw materials, and 2.16 × 10 ^-5 mol / min and 2.64 respectively.
The flow rate was fixed at × 10 ^-5 mol / min. Phosphine (PH ₃ ) was used as the group V raw material, and the flow rate of PH ₃ was changed to set the respective values of the (group V flow rate) / (group III flow rate) ratios of 66, 120, 230, 410. Growth temperature is 600 ℃, 650 ℃, 700 ℃, 750
Performed at ° C. The energy gap obtained by photoluminescence measurement at room temperature of Ga _0.5 In _0.5 P crystal grown by combining the above V / III ratio and the growth temperature is as shown by the mark in the figure. It was a point. In addition, the above Ga obtained by the double crystal X-ray diffraction method
The composition of _0.5 In _0.5 P of Ga and In was within 0.3% from the lattice matching with the GaAs substrate, and the deviation was small.

The above relationship between V / III ratio, growth temperature and energy gap was obtained with good reproducibility. Within the above range, Ga _0.5 In
The electrical and optical properties of _0.5 P were not compromised.
Ga grown at a growth temperature of 700 ° C and a V / III ratio of 400
_{By using 0.5} In _0.5 P for the active layer of the double heterostructure (DH) laser, CW oscillation was achieved at room temperature with an oscillation wavelength of 6890Å. Also, G grown at a growth temperature of 700 ° C and a V / III ratio of 66
a DH laser with _0.5 In _0.5 P active layer, oscillation wavelength 6700Å
The room temperature CW oscillation was achieved.

(Effects of the Invention) The energy gap obtained by photoluminescence measurement of Ga _0.5 In _0.5 P crystal lattice-matched to a GaAs substrate can be controlled by this method without changing the composition of Ga _0.5 In _0.5 P. In addition, the oscillation wavelength of the AlGaInP semiconductor laser can be controlled accordingly.

[Brief description of drawings]

The figure shows the relationship between the growth temperature of Ga _0.5 In _0.5 P lattice-matched to a GaAs substrate, the V / III ratio, and the peak energy obtained from photoluminescence measurements.

Claims (1)

[Claims] 1. A growth temperature and a ratio of a group V element to a group III element of a source gas are adjusted so that a desired energy gap is obtained.
(700,60,1.895), (700,230,1.86), (700,410,1.8)
5), (750,230,1.895), (650,230,1.86), (600,23)
Expression passing through each point (0,1.865) And GaAs by organometallic pyrolysis
Growth method of Ga _0.5 In _0.5 P crystal and growing the Ga _0.5 In _0.5 P crystal lattice matched to the substrate.