JP2727944B2 - Method of manufacturing semiconductor laser array - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a high-power semiconductor laser used for measurement, processing, and the like.

[0002]

2. Description of the Related Art As a light source for optical measurement, particularly for distance measurement,
The development of high-power semiconductor lasers having a wavelength of 1 μm or more is in progress. There are several methods for increasing the output of a semiconductor laser, but the most typical one is a structure in which laser elements alone are arranged in an array and current is uniformly injected. As a conventional report example, as shown in FIG. 4, the active layer 4 is formed without interruption, and a ridge guide structure (NK Dutta et al., In which a p-type InP clad layer 7 is formed in an array).
Applied Physics Letters, v
ol. 46, pp. 803 (1985)) or an embedded ridge structure (M. Razeghi et al., Applier) in which active layers 4 are formed in an array as shown in FIG.
d Physics Letters, vol. 50,
pp. 230 (1987)). In such an array structure, a single stripe structure element having a refractive index waveguide structure is optically weakly coupled, and an outgoing beam with a uniform emission angle and a narrow emission angle can be obtained. The light output increases as the number of arrays increases.
W is reported, and in the latter case, a CW output of 0.12 W and a pulse peak output of 0.3 W are reported.

[0003]

Since such a high-power array semiconductor laser has a wide light emitting area and a current flows into a plurality of stripe structures uniformly, it is important to form a high-quality active layer uniformly. It is. Further, in order to obtain a smooth and narrow beam pattern with good reproducibility, it is necessary that each stripe structure has the same shape.

However, in the conventional manufacturing method, an etching step of the semiconductor layer is required to form such a stripe structure. That is, in the device of FIG.
The ridge structure is formed by etching the clad layer right above the active layer. In the device of FIG. 5, a plurality of stripe structures are formed by etching after growing the active layer over the entire surface. In element formation by such etching, variations in etching depth and side etching amount are inevitable,
It has been difficult to produce a uniform array structure with good reproducibility.

As a method of manufacturing a semiconductor laser without etching a semiconductor, there is a method by selective growth (see Sasaki et al., JP-A-4-105383 (Japanese Patent Application No. 2-22).
2928)). In this method, as shown in FIG. 6, after forming a pair of dielectric thin film stripes 21 as growth inhibition masks at regular intervals on the surface of a semiconductor substrate, a semiconductor multilayer film including an active layer is selectively laminated, and a pair of dielectric thin films is formed. The multilayer film formed in the waveguide region 22 sandwiched between the thin film stripes 21 is used as an optical waveguide structure of a semiconductor laser or the like. When this method is used, the waveguide structure can be formed only by forming a thin film stripe without etching the semiconductor, so that there is a feature that the uniformity and the reproducibility are excellent.

However, the purpose of these inventions is to manufacture a single semiconductor laser, and a pair of dielectric thin film stripes 21 are formed at regular intervals. Therefore, it cannot be applied to the manufacture of a semiconductor laser array.

[0007]

Means for solving the above problems are as follows.

The method further comprises forming a plurality of dielectric thin films in the form of stripes on the surface of the semiconductor substrate, and selectively forming a semiconductor multilayer structure including an active layer in a region sandwiched between the dielectric thin film stripes. The width and the interval of the dielectric thin film stripes are constant, and a plurality of semiconductor multilayer structures selectively formed in a region interposed between the dielectric thin film stripes. A method for manufacturing a semiconductor laser array, comprising a step of forming a semiconductor cladding layer so as to cover the same.

In the above-described method for manufacturing a semiconductor laser array, a semiconductor multilayer film and a semiconductor clad layer are laminated after forming a diffraction grating on a part of the surface of a semiconductor substrate, and the electrode is not formed as a region where the diffraction grating is formed. And a method of manufacturing a semiconductor laser array.

[0010]

In the conventional device manufacturing method using selective growth as shown in FIG. 6, only the waveguide region 22 sandwiched between a pair of thin film stripes 21 is used as an active layer, and the other growth regions are used for the device. Could not be included. On the other hand, the present invention is characterized in that the thin film stripes 21 having a constant width and a constant interval are formed periodically, and all the selectively formed semiconductor multilayer films are used as the active layers of the semiconductor laser array.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example in which a semiconductor laser array is manufactured using the present invention will be described below. FIG. 1 is a sectional view showing a manufacturing process of a semiconductor laser array. First, as shown in FIG. 1A, the surface of a (100) -oriented n-type InP substrate 1 is
An iO ₂ film 21 was formed and processed into a periodic stripe in the [011] direction. The SiO ₂ stripe width was 4 μm, and the interval was 4 μm. Next, as shown in FIG.
P clad layer 2 (layer thickness 0.1 μm), InGaAs / I
Active layer 4 having an nGaAsP multiple quantum well structure (well layer thickness 7 nm, barrier layer thickness 10 nm, number of wells 5), p-type I
A semiconductor multilayer structure composed of the nP cladding layer 6 (layer thickness: 0.1 μm) was selectively formed. For the crystal growth, metal organic chemical vapor deposition (MOVPE) was used. Next, as shown in FIG. 1C, the SiO ₂ stripe 21 is removed, and a p-type InP cladding layer 7 (layer thickness 1.5 μm) and a p-type InGaAs cap layer 8 (layer thickness 0.3 μm) are formed on the entire surface. did. A p-side electrode 11 and an n-side electrode 12 are formed on both surfaces and have a thickness of 10
It was cut out to 0 μm, 600 μm in length, and 300 μm in width, mounted on a diamond heat sink, and evaluated for characteristics. The threshold current of the device was 400 mA, and a maximum CW output of 700 mW was obtained in a state where both ends were cleaved. The full width at half maximum of the far-field image was 3 ° in the horizontal direction and 35 ° in the vertical direction, and a single-peak beam having a uniform phase was obtained. Of 100 devices cut out from the same wafer, 80% of the devices had a CW output of 500 mW or more, and 75% of devices had a full width at half maximum of 5 ° or less in the horizontal direction, showing high uniformity.
It is considered that such high uniformity is due to the fact that the present element is formed uniformly by selective growth.

Next, an example in which a device in which a master laser array and an optical amplifier are integrated is manufactured will be described. FIG. 2 shows a perspective view of the element. The elements are a master laser unit 31, a separation unit 3
2 and an optical amplifier 33. First, after forming the diffraction grating 23 only on the master laser part 31 on the surface of the n-type InP substrate 1, a multilayer structure including the n-type InGaAsP guide layer 3 and the active layer 4 is selectively formed, and the p-type InP clad layer 7 is formed. The p-side electrode 11 has a structure in which the master laser unit 31 and the optical amplification unit 33 are independent from each other. When forming such an integrated device,
As a mask pattern at the time of growing the active layer, there is a method of forming a uniform pattern in each region as shown in FIG. 3A, but here, as shown in FIG. Although the width of the formed waveguide region 22 was fixed, the waveguide region 22 was formed in a pattern in which the waveguide region 22 spreads in a tapered shape and is coupled to each other in the optical amplifier 33. Devices integrating such a tapered optical amplifier and a single-stripe laser have already been reported, for example, in Electronics Letters, vol.
28, p. 201 (1992)), a high light output is obtained while maintaining the single transverse mode. In this example, an element in which an array semiconductor laser and an optical amplifier were integrated was manufactured. The manufacturing process is almost the same as that of the device shown in FIG. 1, but the crystal growth was performed by a gas source molecular beam epitaxy method using atomic hydrogen irradiation. The p-side electrode and the InGaAs cap layer 8 are formed outside the waveguide region 22 and in the separation portion 32.
Then, it was removed by etching, so that current flowed only in the waveguide region 22. The length of each area is the master laser 3
1 is 500 μm, the separation unit 32 is 20 μm, and the optical amplification unit 33
Was 1 mm.

The oscillation threshold current of the laser is 60 mA,
By injecting 2 A of current into the optical amplifier, a maximum CW output of 800 mW was obtained. The radiation beam was monomodal and stable with increasing light output.

[0014]

As described above, by using the semiconductor laser array manufacturing method of the present invention, the array structure can be formed with high uniformity and reproducibility by selective growth without using semiconductor etching. It became so. In the embodiment, an example of manufacturing an InGaAsP / InP-based laser element on an InP substrate has been described.
The same effect can be obtained by the same method in a device of GaAs or InGaAs / GaAs material.

[Brief description of the drawings]

FIG. 1 is a sectional view illustrating a method for manufacturing a semiconductor laser array according to the present invention.

FIG. 2 is a perspective view showing a structure of an integrated element of a semiconductor laser array and an optical amplifier according to the present invention.

FIG. 3 is a front view of a mask pattern showing a method for manufacturing an integrated device of a semiconductor laser array and an optical amplifier according to the present invention.

FIG. 4 is a cross-sectional view showing a structure of a semiconductor laser array according to a conventional invention.

FIG. 5 is a sectional view showing a structure of a semiconductor laser array according to a conventional invention.

FIG. 6 is a cross-sectional view illustrating a method for manufacturing an optical semiconductor device by selective growth according to a conventional invention.

[Explanation of symbols]

0 n-type InP substrate 1 n-type InP clad layer 3 n-type InGaAsP guide layer 4 active layer 5 p-type InGaAsP guide layer 6 p-type InP clad layer 7 p-type InP clad layer 8 p-type InGaAs cap layer 11 p-side electrode 12 n Side electrode 21 SiO ₂ film 22 Waveguide region 23 Diffraction grating 31 Master laser unit 32 Separation unit 33 Optical amplification unit

 ────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-5-243673 (JP, A) 1993 IEICE Autumn Conference C-98 4-178 APPL. PHYS. LETT. 50 (1987) p. 230 APPL. PHYS. LETT. 46 (1985) p. 803 1993 IEICE Autumn Conference C-100 4-180

Claims (2)

(57) [Claims] 1. A semiconductor laser having a step of forming a plurality of dielectric thin films in a stripe shape on a surface of a semiconductor substrate and selectively forming a semiconductor multilayer structure including an active layer in a region sandwiched between the dielectric thin film stripes. Forming a semiconductor cladding layer so as to cover a plurality of semiconductor multilayer structures selectively formed in a region sandwiched between the dielectric thin film stripes, while keeping a constant width and spacing of the dielectric thin film stripes. A method for manufacturing a semiconductor laser array, comprising the steps of: 2. In the method of manufacturing a semiconductor laser array, a semiconductor multilayer film and a semiconductor clad layer are laminated after forming a diffraction grating on a part of the surface of a semiconductor substrate, and electrodes are not used as regions where the diffraction grating is formed. 2. The method for manufacturing a semiconductor laser array according to claim 1, wherein the semiconductor laser array is formed by being divided into regions.