JP2689471B2 - Array type semiconductor laser manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an array type semiconductor laser suitable for optical information processing.

(Prior Art) Conventionally, in a semiconductor laser, for the purpose of increasing the output and preventing deterioration of the end face of the resonator, the emission end face portion is tuned to the oscillation wavelength,
A structure is considered in which a transparent window region is provided to avoid absorption of oscillation light at the end face. As one of such structures, a structure is known in which both ends of the resonator are filled with a composition having a higher Al mixed crystal ratio than the active layer.

For example, "Large Optical AlGaAs Embedded Heterostructure Window Laser" proposed by Blaubert et al. In Applied Physics Letter Volume 40 in 1982 ("Large Optical
cavity AlGaAs furied heterostructure window laser
s "Appl.phys.Lett.vol 40.p1020) shows the schematic structure of the cross section in the cavity direction in Fig. 5.

Laser structure of FIG. 5 is a liquid-phase growth method, P-Al _y G
a _1-y As After continuously growing up to the optical guide layer 34, the n-type GaAs substrate 31 is removed by etching at 25 μm in the vicinity of the resonator end, and the Al mixed crystal ratio is smaller than that of the cladding layer 32.
High resistance light window regions 38 and 39, which have a larger Al liquid crystal ratio than 34,
The active layer 33 is embedded in the cavity direction. The structure of FIG. 5 has a region that does not absorb light generated by recombination of carriers, so that the output can be increased and the end face breakdown level can be improved from several tens mW to 150 mW.

(Problems to be solved by the invention) In the structure of FIG. 5 in which both ends of the resonator are filled with crystals having a higher Al mixed crystal ratio than the active layer, the crystallinity deterioration of the growth layer interface and the embedded edge face, the vertical shape of the interface Deviation from the above results in reflection loss, deteriorating the laser characteristics, and the reliability of the device cannot be sufficiently obtained.

Therefore, an object of the present invention is to eliminate these drawbacks and to provide a method of manufacturing a high-power semiconductor laser having a mode-controlled single-growth window region.

(Means for Solving the Problem) The means provided by the present invention for solving the above-mentioned problems is that a III-V group polycrystal active layer is provided on a semiconductor substrate and is adjacent to the active layer. Two stripe-shaped light emitting regions, a light emitting stripe I and a light emitting stripe II, are formed, and the light emitting stripe I reaches an active region where laser light is generated by laser oscillation and both ends of the active region to a light emitting end face. A method for manufacturing an array type semiconductor laser comprising a window region occupying a space, wherein a multilayer semiconductor layer including the active layer is formed by crystal growth by a metal organic chemical vapor deposition method, and the active layer growth step is performed. In order to grow crystals by selectively irradiating laser light with a mask, the mask uses the window region of the light emitting stripe I and the light emitting stripe II.
Has a pattern of irradiating the laser beam over the entire area of
The light emitting end face is formed by cleavage.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing the structure of an array type semiconductor laser manufactured by the method of one embodiment of the present invention, FIG. 2 is a process drawing showing the manufacturing method of the embodiment, and FIG. 4) is a perspective view showing the process of FIG. 4) in an easy-to-understand manner, and FIG. 4 is a conceptual view showing a crystal growth method used in the embodiment.

In the manufacturing method of this embodiment, first, on a (100) p-type GaAs substrate (Zn-doped p-type impurity concentration 1 × 10 ¹⁹ cm ⁻³ ) 1, a reduced pressure MOVPE growth technique with a growth temperature of 650 ° C. and a growth pressure of 50 torr is used. p-type Al _0.55 Ga _0.45 As clad layer 2 (zinc-doped, p
Type impurity concentration 1 × 10 ¹⁸ cm ⁻³ ) 2 μm, p-type Al _0.4 Ga _0.6
As optical guide layer 3 (zinc-doped, p-type impurity concentration 7 × 10 ¹⁷
cm ⁻³ ) is 0.5 μm, and is successively grown without light irradiation (FIG. 2 (a)).

Next, with an excimer laser (output 1.5 W / cm ² , pulse energy density 30 mJ / cm ² , wavelength 193 nm), as shown in FIG. 4, p on the susceptor 51 is selectively passed from outside the reaction tube 52 through the mask 52. The crystal is grown while irradiating the type GaAs substrate 1 with light. A selective light irradiation pattern is used in this crystal growth. In the selective light irradiation pattern, the third
As shown in the figure, the non-light-irradiated area portion corresponds to the active area of the light-emitting stripe I when the array laser is formed, while the light-irradiated area portion corresponds to the window area of the light-emitting stripe I and the entire light-emitting stripe II.

In the following steps, the layer thickness of each layer is controlled by the layer thickness of the non-irradiated portion. Low pressure MOVPE growth with selective light irradiation at 100 μm width and 300 μm intervals, and further 500 Å of active layer 4
(Non-doped), n-type Al _0.55 Ga _0.45 As cladding layer 5 (silicon-doped, n-type impurity concentration 1 × 10 ¹⁷ cm ^-3 ), n ^{+ -type} Ga
As cap layer 6 (silicon-doped, n-type impurity concentration 3 ×
10 ¹⁸ cm ⁻³ ) of 0.5 μm is successively grown continuously (FIG. 2 (b), FIG. 3).

Next, an insulating film is formed by CVD to 5000 Å, and a striped insulating film 21 having a width of 5 μm is left in parallel with the cavity direction by a photolithography technique. A Ga ⁺ ion beam (dose amount 4 × 10 ¹⁴ cm ^-2 ) is injected up to at least the p-type cladding layer 2 from above the insulating film, and annealed at 700 ° C. for 20 minutes to form the insulating film 2
1 is removed (Fig. 2 (c)).

The insulating film is formed again by CVD to 3000 Å, and the insulating film 7 is left by 50 μm wider inward than the stripe width formed by the light irradiation by the photolithography technique, perpendicularly to the cavity direction (Fig. 2 (d )).

Next, the striped n-type electrode 8 is selectively formed by ion milling and photolithography, and the p-type electrode 9 is formed on the back surface (FIG. 2 (e)). The array type semiconductor laser of FIG. 1 is obtained by the above steps. This array type semiconductor laser has a plurality of light emitting regions, and one of the light emitting regions (wavelength λ ₂ ) has a window region at the end face portion.

(Effects of Embodiment) The operation of the semiconductor laser having the structure of FIG. 1 manufactured in the above embodiment will be described below. It is known from the report by Hirayama et al. That the n-type region implanted with Ga ⁺ ion beam has a high resistance (The Journal of Applied Physics, Vol.
earned Implanted GaAs Epilayer "), carriers injected from the p-type electrode 9 are not injected into the ion-implanted region 10 but are concentrated in the stripe-shaped active region in the center of the resonator. Of Al _x Ga _1-x As under reduced pressure (50torr) on the non-irradiated area, Δx = 0.02
~ 0.05 change, the decomposition efficiency of the organic metal trimethylaluminum increased by the excimer laser irradiation,
An increase in the Al mixed crystal ratio was reported by Hiiragimoto et al. In 1986, Journal of Crystal Growth, Vol. 77, p. 223 (“J. Crystal.
Growth, 77, P223, (1986) "Selective Area Control of
Material Properties in laser-Assisted NOVPE of Ga
As and AlGaAs ").

When the Al mixed crystal ratio is 0.4 or more, the mixed crystal ratio is changed by 0.04 to 0.05 by irradiating the excimer laser beam. The n-Al _0.55 Ga _0.45 As cladding layer was 2 μm under the irradiation of excimer laser light.
m is formed, a tapered stripe pattern is formed between the irradiated portion and the non-irradiated portion due to the difference in growth rate,
This can be used for mask alignment.

Therefore, the Al mixed crystal ratio of the active layer 4 is 0.15, and it is estimated from the change of the Al mixed crystal ratio between the irradiated portion and the non-irradiated portion that ΔEg> 50 meV.
Thus, the irradiated portion acts as a window for the light generated by the recombination of carriers, and the level of the end face breakdown of the resonator is increased. Further, the irradiated portion and the non-irradiated portion are coupled in a tapered shape, and the light guide layer 3 below the active layer 4 is formed.
Up to the growth, the entire wafer is non-irradiated and no step deviation occurs at the joint portion. Therefore, according to the manufacturing method of this embodiment, the reflection loss at the coupling portion is poor and the window region can be formed. High output operation can be expected in the semiconductor laser of FIG. 1 manufactured in this way. Further, in the method of the embodiment, a semiconductor laser can be obtained by a single crystal growth,
The fabrication process does not expose the edges of the active area to air. Therefore, the manufactured semiconductor laser can be expected to have high reliability without the problem of interface deterioration.

Further, in the array type semiconductor laser of FIG. 1, the wavelength of the laser light generated from the adjacent light emitting regions is such that when the wavelength of the non-light irradiation portion, that is, the light emitting stripe I is 780 nm, the light irradiation portion, that is, light emitting stripe II. Is the wavelength of
It is shorter than 755 nm and Δλ> 25 nm can be expected. As described above, the array-type semiconductor laser according to the present invention is a multi-wavelength type, and crosstalk hardly occurs even when it is applied to an information processing device and writing and reading are performed in parallel.

(Effects of the Invention) According to the method of the present invention, as described above, single growth has a window region in the vicinity of both end faces of the resonator, and this window region is coupled with the active region in a tapered shape, There is also no reflection loss at the coupling portion between the window region and the active region, and a mode-controlled high-power highly-reliable semiconductor laser can be formed as one emission stripe of an array-type semiconductor laser, and therefore, the method of the present invention is applied, It is possible to manufacture an array type semiconductor laser in which the emission wavelengths of adjacent light emitting regions are different from each other.

When the array type semiconductor laser manufactured by the method of the present invention is used as a light source of an information processing device, crosstalk is unlikely to occur even when data writing and reading are performed in parallel.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an array type semiconductor laser manufactured by a method of an embodiment of the present invention, FIG. 2 is a manufacturing process drawing of the embodiment, and FIG. 3 is a drawing of FIG. 2 (b). It is a perspective view showing a process easily. FIG. 4 is a conceptual diagram showing a selective light irradiation method, and FIG. 5 is a sectional view showing a structure of a conventional window structure laser. 1 ... p-GaAs substrate, 2 ... p-Al _0.55 Ga _0.45 As clad layer, 3 ... p-Al _0.4 Ga _0.6 As optical guide layer, 4 ... Al
_0.15 Ga _0.85 As active layer, 5 ... n-Al _0.55 Ga _0.45 As clad layer, 6 ... n ⁺ -GaAs cap layer, 7 ... Insulating film, 8 ...
... n-type electrode, 9 ... p-type electrode, 10 ... Ga ⁺ ion beam implantation region, 21 ... insulating film, 31 ... n-type GaAs substrate, 32 ...
n-type Al _x Ga _1-x As clad layer, 33 …… active layer, 34 …… p-type
Al _y Ga _1-y As optical guide layer, 35 ...... p-type _{Al x 'Ga 1-x'} As
Cladding layer, 36 ... n-type GaAs block layer, 37 ... Zn diffusion region, 38,39 ... Al _z Ga _1-z As window region, 40 ... p-type electrode, 4
1 ... n-type electrode, 42 ... insulating film, 51 ... susceptor, 52 ...
… MOVPE reaction tube, 52 …… mask, 54 …… mirror, 55 ……
Excimer laser light.

Claims (1)

(57) [Claims] 1. A semiconductor substrate is provided with an active layer of a group III-V multi-element crystal, in which two adjacent striped light emitting regions, a light emitting stripe I and a light emitting stripe II are formed. In the method for manufacturing an array type semiconductor laser, the light emitting stripe I comprises an active region for generating a laser beam by laser oscillation and a window region occupying between both ends of the active region to a light emitting end face. Is formed by growing a crystal by a metal organic chemical vapor deposition method. In the step of growing the active layer, the mask is selectively irradiated with laser light to grow the crystal. The array type semiconductor is characterized in that the window region of the light emitting stripe I and the entire region of the light emitting stripe II are patterned to irradiate the laser light, and the light emitting end face is formed by cleavage. Body laser manufacturing method.