JP2883426B2 - Method for growing compound semiconductor crystal - Google Patents

Description

The present invention relates to a method for growing a compound semiconductor crystal for growing a GaInP crystal or AlGaInP crystal on a GaAs substrate by using the MOCVD method.

(B) Conventional technology AlGaInP-based compound semiconductors have a wavelength in the 0.6 μm band and are used as materials for visible light semiconductor lasers.

For the growth of such AlGaInP compound semiconductors, for example, Journal
of the Crystal Growth, 68 (1984), pp. 483 to 489, the MOCVD method (metal organic chemical vapor deposition) is used, and the growth conditions are as shown in Table 1.

On the other hand, in the visible light semiconductor laser, there is a demand for further shortening of the wavelength.
No., Japanese Patent Application No. 1-83107, from GaAs (100 faces) <011>
It has been proposed that the wavelength can be shortened by using a plane 5 to 7 ° off in the direction as a crystal growth plane.

(C) Problems to be Solved by the Invention However, even if the GaAs substrate is turned off at 5 to 7 ° C., a semiconductor laser using GaInP as an active layer is manufactured thereon. About 656-660nm,
No shorter wavelength could be obtained.

Accordingly, the present invention provides a method for growing a compound semiconductor crystal that can further shorten the wavelength.

(D) Means for Solving the Problems The present invention is a method for growing a compound semiconductor crystal for growing a GaInP crystal or an AlGaInP crystal on a GaAs substrate by MOCVD. The crystal growth plane whose plane orientation is inclined by 5 to 7 ° from the (100) plane in the <011> direction is used, and the growth rate is 4 °.
1010 μm / hr.

(E) Function According to the method of the present invention, the band gap of the compound semiconductor crystal grown on the GaAs substrate is further widened.

(F) Example The present invention is based on the phenomenon first discovered by the present applicant that the band gap of an AlGaInP-based compound semiconductor depends on the plane orientation of a GaAs substrate, and furthermore, the growth rate in this plane orientation is determined by the growth rate. Was also made by finding that the band gap changed.

FIG. 1 shows the experimental results of examining the growth rate dependence of the band gap. In this experiment, the crystal orientation of the crystal growth surface of the GaAs substrate was set to a plane inclined by 5 ° and 7 ° from the (100) plane to the <011> direction, and a GaInP crystal was grown thereon by MOCVD using MOCVD. Are varied and each is grown, and its PL (photoluminescence) peak energy is examined. In such growth, the growth temperature is 650 ° C. and the growth pressure is 70 Tor.
The substrate was rotated at 8 rpm in the reaction chamber in order to achieve more uniform growth with the r / V / III raw material supply ratio set to 550. Also,
Each growth rate was set by changing the supply amount of the source gas.

From FIG. 1, it can be seen that the PL peak energy becomes substantially maximum when the growth rate is 4 μm / hr or more, and a sufficiently large PL peak energy is obtained as compared with the conventional case where the growth rate is 1.5 μm / hr. 5μm / hr or more, 4μ when tilted 7 °
At m / hr or more, it can be seen that the PL peak energy is 1.92 eV, which is the band gap of GaInP bulk. The growth rate dependence of such PL peak energy is
It also appears in (Al _x Ga _1-x ) InP crystal (0 ≦ x ≦ 0.5),
Substantially the maximum PL peak energy of each crystal was obtained at 4 μm / hr or more as in the case of the GaInP crystal. Here, although not shown in the figure, in either case of the inclination angle, when the growth rate exceeded 10 μm / hr, the surface of the growth layer became uneven, and a favorable surface state could not be obtained. Therefore, the growth rate needs to be 10 μm / hr or less in consideration of the surface state of the growth layer.

When the inclination angle of the substrate is smaller than 5 °,
The growth rate at which the PL peak energy increases becomes 10 μm / hr or more, and only the growth layer having a poor surface condition can be obtained.

Next, using a GaAs substrate in which the plane orientation of the crystal growth plane is inclined by 5 ° and 7 ° in the <011> direction from the (100) plane, the growth rate is changed variously on this, as shown in FIG. , Resonator length 30
An AlGaInP-based semiconductor laser having a thickness of 0 μm was fabricated, and the wavelength during continuous oscillation was examined. FIG. 3 shows the results.

In the semiconductor laser shown in FIG. 2, (1) is a substrate made of n-type GaAs, and one main surface (1a) of the substrate is <011 from the (100) plane.
> 5 ° or 7 ° in the direction. (2) is n
Buffer layer composed of Ga _0.5 In _0.5 P, and (3) is an n-type (Al
_0.6 Ga _0.4 ) _0.5 In _0.5 P n-type cladding layer, (4)
Is an active layer made of undoped Ga _0.5 In _0.5 P, and (5) is p
Type (Al _0.6 Ga _0.4 ) p-type cladding layer composed of _0.5 In _0.5 P,
(6) is a contact layer made of p-type Ga _0.5 In _0.5 P. These layers are formed by MOCVD at a growth temperature of 650 ° C. and a growth pressure of
Under the growth conditions of 70 Torr and V / III supply ratio of 550, the above substrate (1)
Continuously grown on one main surface (1a) of The growth rate at this time is kept constant throughout each layer. Further, the p-type cladding layer (5) and the contact layer (6) are formed by selectively etching away from the surface of the contact layer (6) to the inside of the p-type cladding layer (5) and extend in the direction perpendicular to the drawing. An existing stripe-shaped ridge (7) having a top (7a) having a width of about 5 μm is formed.

(8) a block layer made of n-type GaAs formed on the p-type cladding layer (5) except on the contact layer (6);
(9) is a cap layer made of p-type GaAs formed on the contact layer (6) and the block layer (8).

 Table 2 shows the carrier concentration of each layer.

(10) is a p-side electrode in which a Cr film and an Au film are mounted in this order on a cap layer (9), and (11) is the other main surface (1) of the substrate (1).
b) An n-side electrode on which a Cr film, a Sn film, and an Au film are applied in this order.

Thus, looking at the experimental results in FIG. 3, the oscillation wavelength at the conventional growth rate, that is, about 660 nm at 1.5 μm / hr, was about 650 nm at the growth rate of 4 μm / hr or more. It can be seen that the wavelength can be obtained and the wavelength can be shortened.

The oscillation threshold current and the maximum oscillation temperature of a semiconductor laser manufactured at a growth rate of 4 to 10 μm / hr were both 50 mA,
The temperature was 80 to 90 ° C., which was almost the same as the characteristics of the conventional AlGaInP semiconductor laser. Further, each semiconductor laser produced at a growth rate of 4 to 10 μm / hr was subjected to a constant output continuous operation test of 3 mW at a temperature of 40 ° C., and it was operated stably for 1000 hours or more.

In the method of the present invention, the inclination angle of the substrate must be 5 ° to 7 °. This is because if the tilt angle of the substrate is smaller than 5 °, the surface condition of the growth layer is deteriorated as described above, and if the tilt angle of the substrate exceeds 7 °, the oscillation threshold of the semiconductor laser to be manufactured is increased. This is due to the fact that the current increases significantly and becomes impractical.

Above, in this embodiment, although the active layer of the semiconductor laser shown in FIG. 2 (4) was Ga _0.5 In _0.5 P, this (Al _x G
a _1-x ) _0.5 In _0.5 P (0.05 ≦ x ≦ 0.2)
A similar shortening of the wavelength could be achieved at a growth rate of 4 to 10 μm / hr.

(G) Effects of the Invention According to the method of the present invention, GaI is deposited on a GaAs substrate by MOCVD.
When growing an nP crystal or an AlGaInP crystal, a crystal whose growth direction is inclined from the (100) plane by 5 to 7 ° in the <011> direction is used as the substrate, and the growth rate is 4 to 4. By setting the thickness to 10 μm / hr, the band gap of the growth layer is widened while the surface state of the growth layer is good, and the wavelength can be shortened when applied to a semiconductor laser.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing the dependence of the band gap on the growth rate, FIG. 2 is a cross-sectional view showing the structure of the AlGaInP-based semiconductor laser used in this embodiment, and FIG. FIG.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C30B 1/00-35/00 H01L 21/205 H01S 3/18

Claims (1)

(57) [Claims] 1. A compound semiconductor crystal growth method for growing a GaInP crystal or an AlGaInP crystal on a GaAs substrate by MOCVD, wherein said substrate has a crystal growth plane in a <011> direction from a (100) plane. A method for growing a compound semiconductor crystal, characterized in that a crystal tilted at 5 to 7 ° is used and the growth rate is 4 to 10 μm / hr.