JPH0138390B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a transverse mode control semiconductor laser device using an _{AlGaAs -} based material.

(Prior Art) An example of a conventional transverse mode control semiconductor laser device is as shown in _{FIG .}
type Al _z Ga _1-z As cladding layer 2, p-type Al _w G _a1-w As active layer 3, p-type Al _x G _a1-x As optical waveguide layer 4, n-type Ga _{A s}
Current confinement layer 5, p-type Al _y G _a1-y As cladding layer 6,
It is _constructed by stacking p-type _GaAs contact layers 7.

(Problems to be Solved by the Invention) When manufacturing the above-mentioned transverse mode control semiconductor laser device by the organic metal vapor phase epitaxial (OMVPE) growth method, n-type Al _z is grown on the n-type Ga _{A s} substrate 1.
A Ga _1-z As cladding layer 2, a p-type Al _w Ga _1-w As active layer 3, a p-type Al _x Ga _1-x As photoconductive wave layer 4, and an n-type _{Ga As} current confinement layer 5 are laminated, Next, the current confinement layer 5 is selectively etched to expose the p-type Al _x Ga _1-x As optical waveguide layer 4, and then the p-type Al A method is adopted _in which _{a y} Ga _1-y As cladding layer 6 and a p-type Ga _As contact layer 7 are laminated.

That is, a manufacturing method using so-called two-time OMVPE growth is adopted, but in this case, after the optical waveguide layer 4 is partially exposed to the atmosphere by etching, p-type Al _y Ga _1-y As is deposited thereon. In order to laminate the cladding layer 6,
A drawback is that a high resistance portion is easily formed at the interface between the optical waveguide layer 4 and the cladding layer 6 due to oxidation.

In _{addition ,} when manufacturing a transverse _mode control semiconductor laser device as shown in _FIG. After forming a thin film of n-type _Ga
The A _s current confinement layer 5 is laminated, and then the current confinement layer 5 is etched _{, leaving the above Ga s thin film, and during the next growth, the Ga s thin film} is evaporated at _a high temperature under As pressure. A method of laminating a p-type Al _y Ga _1-y As cladding layer 6 is adopted.

This method is the same as the OMVPE growth method described above in that a transverse mode control semiconductor laser device is manufactured by two epitaxial growth steps, but the photoconductive wave layer 4 is covered with _{a GaAs} thin film until the next growth. Therefore, it is rare for a high-low resistance portion to remain at the interface between the photoconductive wave layer 4 and the cladding layer 6.

However, in this method, the thin film of Ga _As is evaporated at high temperature (750° C.) in a short time (~10 minutes), so precise temperature control of _the substrate temperature and control of the thickness of the thin film are required. In addition, the underlying Al _x Ga _1-x
When x of As is larger than 0.4, there is a disadvantage that a high resistance layer is formed due to oxidation of the base.
It becomes difficult to shorten the oscillation wavelength (740 nm or less).

The purpose of this invention is to use AlG _{a As} based material,
The object of the present invention is to solve the above-mentioned problems that occur when manufacturing, for example, a transverse mode controlled internal stripe semiconductor laser device by epitaxial growth.

(Means for Solving the Problems) For this purpose, the present invention provides a semiconductor laser using an AlG _{a As} material, which has an optical waveguide layer, a current confinement layer, and a clad layer stacked therein as described above. In this step, a coating layer is formed on the optical waveguide layer, a current confinement layer is grown on the coating layer, the current confinement layer is selectively etched, and then the etched portion of the coating layer is heated to a normal growth temperature. The present invention proposes a method for manufacturing the above-mentioned semiconductor laser by evaporating the cladding layer and then growing the cladding layer.

Here, the material suitable for the coating layer is one that can grow a coating layer with a thickness of about 100 Å on the optical waveguide layer at a _temperature higher than the lowest temperature at which _GaAs can grow (450°C), and at a normal growth temperature. It is preferable that it can be evaporated at (approximately 650℃), specifically
One or more In-based compounds such as InAs, InP, and InSb are used.

(Effects of the Invention) In summary, according to the present invention, the current confinement layer is etched leaving the coating layer formed on the optical waveguide layer, and then the coating layer in the etched portion is evaporated at a normal growth temperature. Since the optical waveguide layer is grown, the optical waveguide layer is not exposed to the atmosphere until the next cladding layer grows, and therefore a high resistance part is not generated at the interface between the optical waveguide layer and the cladding layer. .

In addition, since the cladding layer is grown after the coating layer is evaporated at a normal growth temperature, the quantum well structure of the active layer is not destroyed by high temperatures.
Therefore, the semiconductor laser device obtained by the present invention can oscillate in the transverse fundamental mode with low operating current and high output, and has good noise characteristics, so it can be used in digital audio disks, optical disk memories,
Ideal as a light source for laser beam printers, etc.

(Example) The present invention will be explained below based on the illustrated example.

Embodiment 1 FIG. 1 shows an example of the manufacturing process of the present invention. On the (001) plane of an _n -type _GaAs substrate 1, MBE or OMVPE is grown as shown in FIG. 1a. The n-type G _a A _s buffer layer 8 and the n-type Al _x
Ga _1-x As/G _a A _s multiple quantum well buffer layer 9, n
type Al _x Ga _1-x As cladding layer 10, p-type Al _y Ga _1-y As
An active layer 11, a p-type Al _z Ga _1-x As optical waveguide layer 12 , a coating layer 13 , and an n-type Ga _{As current} confinement layer 14 are laminated.

Note that the composition of Al varies depending on the application, but x
>z>y.

The multiple quantum well buffer layer 9 may be omitted in the OMVPE growth method, and the active layer 11 may be either an undoped multiple quantum well (MQW) or a single quantum well (SQW).

The covering layer 13 is formed by growing InAs on the optical waveguide layer 12 to a thickness of about 100 Å at a temperature of about 450°C.

In addition, the n-type _Ga As _current confinement layer 14 has a carrier concentration of 3×10 ¹⁸ cm ^-3 or more and a thickness of approximately
1μm and p for transverse mode control.
The thickness of the Al _z Ga _1-z As optical waveguide layer 12 is made thin (for example, about 0.3 μm) to reduce the effective refractive index in the lateral direction due to the current confinement layer 14 .

Note that Ge, Si, etc. may be thinly laminated on the covering layer 13 as an etching stop layer.

Next, as shown in FIG. 1B, grooves 15 are formed in the current confinement layer 14 in the (110) direction by selective etching.

Note that the width of the groove 15 is set to a width (~3 μm) necessary for transverse mode control, and the coating layer 13 is exposed.

Finally, as shown in FIG. 1c, before growth, the coating layer 13 is evaporated at a temperature of 600°C while applying As pressure, and then the p-type Al _x Ga _1-x As cladding layer 16 and the p-type _Ga
A _s contact layer 17 is grown, and then a p-side electrode 18 and an n-side electrode 19 are formed by vapor deposition.

In the semiconductor laser device manufactured in this way, by grounding the p-side electrode 18 and applying a negative voltage to the n-side electrode 19, the current is constricted by _the n-type _GaAs current confinement layer 14. is implanted into the active layer 11. The light oscillated directly under the groove 15 is absorbed by the n-type _GaAs current confinement layer 14, and a refractive index difference is created in the direction parallel to _the junction surface, thereby ensuring transverse fundamental mode oscillation up to high output.

Example 2 FIG. 2 shows another _{semiconductor laser} device manufactured according to the present invention. G _a A _s buffer layer 8, n-type Al _x Ga _1-x As/
G _a A _s multiple quantum well buffer layer 9, n-type Al _x Ga _1-x
As cladding layer 10, n-type optical waveguide layer 12a (thickness
0.3 μm), undoped single quantum well or undoped multiple quantum well active layer 11a, p-type optical waveguide layer 1
2b (thickness 0.3 μm), coating layer 13 (thickness ~ 100 Å),
An n-type _GaAs current confinement layer 14 _is laminated.

In this case, the n-type to p-type optical waveguide layers 12a, 12
b, as shown in Figure 3, the composition of Al is changed to the active layer 1 in order to achieve good confinement of light and current.
It has a structure in which it gradually decreases toward 1a.

Note that the lowest Al composition x in the n-type to p-type optical waveguide layers 12a and 12b, the number of multiple quantum wells in the active layer 11a, the Al composition and thickness of the barrier, the thickness of the wells, the composition of Al, etc. depend on the application. It is set to oscillate at the lowest threshold current.
Further, the covering layer 13 is formed using an In compound as in Example 1.

Next, a groove 15 is formed in the n-type _{GaAs current} confinement layer 14 by selective etching, and the covering layer 13 is exposed. Finally, before growth, the temperature was raised to 650 while applying As pressure.
After evaporating the coating layer 13 at ℃, p-type Al _x Ga _1-x
As clad layer 16, p-type Ga _{As contact} layer 17
is grown, and then a p-side electrode 18 and an n-side electrode 19 are formed by vapor deposition.

The semiconductor laser device manufactured in this way can be operated in the same manner as in the first embodiment.

[Brief explanation of drawings]

Fig. 1 shows an example of the manufacturing process of the present invention, Fig. 1a shows the first epitaxial growth step, and Fig. 1b shows grooves being created in the current confinement layer by selective etching. Figure 1c is a diagram showing the second epitaxial growth and electrode attachment process, Figure 2 is a perspective view of another semiconductor laser device manufactured according to the present invention, and Figure 3 is the same as above. FIG. 4 is a perspective view showing an example of a semiconductor laser device manufactured by a conventional method. In the figure, 12, 12a, 12b are optical waveguide layers, 13
14 is a current confinement layer, 15 is a groove, and 16 is a cladding layer.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a semiconductor laser using an _{AlGaAs -} based material having a laminated layer of an optical waveguide layer, a current confinement layer, and a cladding layer therein, comprising: forming a coating layer on the optical waveguide layer; A current confinement layer is grown on the coating layer, the current confinement layer is selectively etched, and the coating layer in the etched portion is evaporated at a normal growth temperature before the cladding layer is grown. A method for manufacturing a semiconductor laser characterized by the following.