JPH046113B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a method of manufacturing a semiconductor laser array element in which a plurality of semiconductor laser operating parts emitting oscillations at different wavelengths are arranged in the same element.

<Prior Art> Semiconductor laser array elements in which a plurality of laser oscillation operating units are formed on the same substrate are already known, and this device is provided with operating units that oscillate lasers at the same wavelength. On the other hand, when using a semiconductor laser element as a light source for optical fiber communication, for example, if multiple laser beams with different oscillation wavelengths are coupled to a single fiber and transmitted, the amount of information will be increased in proportion to the number of wavelengths. Many settings can be made, enabling large-capacity optical communication. This is generally referred to as wavelength division multiplexing communication, and is an important development issue for optical fiber communication. In order to couple laser beams of multiple wavelengths into one fiber, it is necessary to place multiple semiconductor laser elements with different wavelengths at one end of the fiber and optically couple them, which makes controllability difficult due to positional accuracy etc. is required. If a single semiconductor laser element could output laser beams with different wavelengths, this problem would be greatly alleviated.

In order to meet these demands, for example, a semiconductor laser array has been proposed in which multiple wavelengths can be obtained by obtaining an active layer with a forbidden band width corresponding to the width of a striped convex portion, as shown in Japanese Patent Laid-Open No. 57-139983. is proposed.

However, when actually manufacturing this conventionally proposed laser array structure, it is necessary to control the degree of supercooling of the melt with a mixed crystal composition, and the mixed crystal ratio of each cladding layer is different. It has been difficult to fully utilize the characteristics of double heterojunction lasers.

<Purpose of the invention> When a ternary or quaternary mixed crystal semiconductor is liquid-phase epitaxially grown on a substrate, the composition ratio of the growth layer changes depending on the growth rate, resulting in an energy band gear. It was found that the two types were different.
(Appliep Letter Physics 42 [5] P.406) That is,
Semiconductor laser devices having active layers manufactured with different growth rates will have different oscillation wavelengths. Taking advantage of this point, the present invention aims to provide a method for manufacturing a new and useful semiconductor laser array element, which has a relatively simple structure and has a plurality of laser oscillation operating parts with different oscillation wavelengths in a single element. It is something.

Another object of the present invention is to provide a method of manufacturing a laser light source that is optimal for wavelength division multiplexing communications.

<Example> FIG. 1 is a perspective view of the structure of a semiconductor laser array device manufactured according to an example of the present invention. This example is a semiconductor laser device with an internal stripe structure (Appl.Phys.Lett.vol.40,
1March1982, P.312).

0.6μm thick n-GaAs on P-type GaAs substrate 1
After growing the current blocking layer 2 by liquid phase epitaxial growth,
a striped groove 3 having widths w ₁ , w ₂ (w ₁ >w ₂ );
4 is formed by a well-known photolithography technique. The current blocking layer 2 is removed inside the striped grooves 3 and 4, and this portion becomes a current path. A p-Ga _1-y AlyAs cladding layer 5, a Ga _1-x AlxAs active layer 6 (0<x<y<
1), n-Ga _1-y AlyAs cladding layer 7, n-GaAs
By sequentially stacking the cap layers 8, a double heterojunction type multilayer crystal layer for laser operation is formed. Next, after lapping the back surface of the substrate 1 to make the wafer thickness approximately 120 μm, a p-side electrode 9 of Au-Zn is formed, while an Au-Zn p-side electrode 9 is formed on the upper surface of the cap layer 8.
- Form an n-side electrode 10 of Ge-Ni. In order to divide the multilayer crystal for laser operation into units of stripe grooves 3 and 4, separation grooves 11 are formed from the surface of the n-side electrode 10 in parallel to the stripe grooves 3 and 4, and the depth thereof is
This multilayer crystal is etched until the GaAs substrate 1 is reached. Through the above steps, a semiconductor laser array element is obtained in which laser oscillation operating portions are formed in regions of the active layer 6 directly above the stripe grooves 3 and 4 having different stripe widths, as shown in FIG. The active layer 6 directly above the stripe groove 3 with a stripe width of w ₁ becomes a thick active part that is curved downward.
On the other hand, the active layer 6 directly above the stripe groove 4 having a stripe width of w ₂ constitutes a flat operating section. That is, since the stripe width is w ₁ > w ₂ , the upper surface of the cladding layer 5 grown on the stripe grooves 3 and 4 is concave in the width w ₁ portion and flattened in the width w ₂ portion. . Therefore, in the active layer 6 deposited on the cladding layer 5, the part of the stripe width _w1 is an epitaxially grown layer whose growth rate is faster than the other part, and constitutes a thick active part of the layer curved downward. The portion w ₂ is an epitaxially grown layer whose growth rate is slower than this and constitutes a flat operating section. As described above, when epitaxial growth is performed from the same growth melt, the composition ratio of the resulting grown layer differs depending on the growth rate. Therefore, in the curved laser oscillation area and the flat laser oscillation area, laser beams with different oscillation wavelengths are emitted due to the difference in energy band gap based on the difference in the mixed crystallization of Ga _1-x AlxAs. It will be output.

The stripe width w ₁ = 8 μm, w ₂ = 4 μm, the distance between the stripe grooves 3 and 4 is 20 μm, and the active layer 6 is
When the Al mixed crystal ratio x = 0.08 and the Al mixed crystal ratio y of the cladding layers 5 and 7 are set to 0.3, the active layer 6 directly above the stripe groove 3 is curved, and the other parts are flattened. It will be done. Further, the epitaxial growth conditions are set so that the thickness of the active layer 6 is at most 0.2 μm in the curved portion and 0.06 μm in the flat portion. As a result, laser output light having a wavelength of 830 nm is obtained in the curved oscillation active portion corresponding to the area directly above the striped grooves 3 and 4 of the active layer 6, and 810 nm in the flat oscillation active portion. Note that the oscillation threshold current is determined by the curved oscillation operating part.
It was 25mA, and 35mA in the flat oscillation area.

Next, the stripe width w ₁ = 6 μm, w ₂ = 3 μm, the interval between the stripe grooves 3 and 4 is 20 μm, the Al mixed crystal ratio of the active layer 6 is x = 0.15, and the cladding layers 5 and 7 are
Set Al mixed crystal ratio y=0.5. The active layer 6 has a thickness of 0.15 μm at the curved portion and 0.04 μm at the flat portion. As a result, a laser output light having a wavelength of 785 nm can be obtained in the curved oscillation operating section. In this case, the oscillation threshold current was 30 mA in the curved oscillation area and 45 mA in the flat oscillation area.

FIG. 2 is a perspective view of a semiconductor laser array device manufactured according to another embodiment of the present invention. In this embodiment, three types of stripe grooves having different widths are carved, and three laser oscillation operating parts having different growth rates are formed on each groove. In the figure, the same reference numerals as in FIG. 1 indicate the same contents.

N-GaAs current blocking layer 2 on P-type GaAs substrate 1
are grown by liquid phase epitaxial growth, with widths w ₁ , w ₂ , w ₃
Three stripe grooves 1 with (w ₁ > w ₂ > w ₃ )
2, 13, and 14 are formed. On top of this the first
As shown in the figure, multilayer crystals for laser operation are stacked and divided into three stripe grooves 12, 13, and 14 by separation grooves 11 and 11' at the center between the stripe grooves. The active layer 6 is largely curved at each stripe width _w1 , slightly curved at each stripe width _w2 , and flattened at each stripe width _w3 . Therefore, in this semiconductor laser array element, three laser output lights having different wavelengths are obtained from the three laser oscillation operating parts.

Although the above embodiment describes a GaAlAs-based semiconductor laser array element, the present invention is not limited thereto, and ternary or quaternary compound semiconductors such as GaAsP, GaInP, InGaAsP, and others may also be used. It is also possible to form four or more laser oscillation operating parts, and the difference in oscillation wavelength is 5 to 5.
It can be set appropriately to about 40 nm.

<Effects of the Invention> As described in detail above, according to the present invention, it is possible to obtain a semiconductor laser array element in which a plurality of laser oscillation operating parts having different oscillation wavelengths are formed in a single element. In addition, the structure utilizes the difference in stripe width to form active layer regions with different growth rates, and a laser light source optimal for wavelength division multiplexing communication is established with a relatively simple structure.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a semiconductor laser array device manufactured according to an embodiment of the present invention. Second
The figure is a perspective view of a semiconductor laser array device manufactured according to another embodiment of the present invention. 1...Substrate, 2...Current blocking layer, 3, 4, 1
2, 13, 14... Stripe groove, 5... P-type cladding layer, 6... Active layer, 7... N-type cladding layer, 8... Cap layer, 9... P-side electrode, 10...
...N-side electrode, 11, 11'...separation groove.

Claims (1)

[Claims] 1. A step of epitaxially growing a GaAs current blocking layer of the opposite conductivity type on a GaAs substrate, and forming a striped groove having at least widths w ₁ and w ₂ (w ₁ >w ₂ ), A step of removing a part of the current blocking layer in a stripe shape, a Ga _1-y Al _y As cladding layer, a Ga _1-x Al _x As active layer (0<x<y<1), a Ga 1-y Al y As cladding layer, a Ga 1-y Al y As clad layer, a Ga _1-y Al _y As clad layer and
A step of sequentially forming a GaAs cap layer by a liquid phase epitaxial growth method, and a step of forming a separation groove in each stripe groove in a manner substantially parallel to the stripe groove until reaching the GaAs substrate. A method for manufacturing a semiconductor laser array element, comprising forming active layers each having a different Al mixed crystal ratio.