JPH01155675A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain laser rays variant in a direction of linear polarization and wavelength by a method wherein two or more semiconductor lasers provided with active layers epitaxially grown through a vapor phase growth are laminated on a substrate provided with surfaces different from each other in a facial index. CONSTITUTION:A resist film is provided onto a P<+>-GaAs substrate 21 whose upper face is a (001) face, and the resist film is removed after the formation of a cutout with an angle of 45 degrees formed through a wet etching on the substrate 21. Next, an epitaxial film 24 and a metal mask 25 are formed, a resist film 26 is formed thereon so as to etch the metal mask 25 using the resist film 26 as a mask, and a Zn diffused region 22 is formed after the removal of the resist film 26. Then, a SiO2 film 12 is formed after the metal mask 25 is eliminated, an Au/Au-Ge layer 11a is evaporated after a current injecting window section is bored, a resist film 27 is formed thereon, an n-side electrode 11 is constructed through etching, and a P-side electrode 13 is provided after the removal of the resist film 27.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a monolithic device that oscillates a plurality of laser beams with different linear polarization directions and oscillation wavelengths, and is suitable for optical measurement, optical multiplex transmission, optical memory, etc. It relates to a semiconductor laser device.

[Prior Art] Conventionally, methods for obtaining multiple laser beams with different polarization directions or oscillation wavelengths can be roughly divided into (1) methods using a semiconductor laser device in which a plurality of separately manufactured semiconductor lasers are hybrid-mounted; 2) A method using a multi-beam semiconductor laser device manufactured through a complicated process such as growing an epitaxial thin film on the north side of the substrate, processing it, and then regrowing it, (3) using multiple semiconductor lasers A method of using a semiconductor laser device combined on the optical path of an optical system using the above is known.

[Problems to be Solved by the Invention] However, in the method (1) above, a high degree of integration is required for positioning each semiconductor laser during hybrid mounting.

In the method (2), the process including various steps of processing after film growth and further regrowth is complicated, and therefore requires high technology and lacks productivity.

The method (3) has the disadvantage that the optical path length becomes large and complicated, and the distance between the semiconductor laser device and the peripheral equipment becomes long.

An object of the present invention is to provide a semiconductor laser device that solves these problems.

[Means for Solving the Problems] The semiconductor laser device of the present invention is a semiconductor laser oscillator that oscillates a plurality of laser beams with different linear polarizations.
It is characterized in that two or more semiconductor lasers each having an active layer formed by vapor phase epitaxial growth are stacked on one or more of the surfaces.

[Operation] As described above, when epitaxial growth (one growth operation is sufficient) is performed on a pre-processed substrate, multiple monolithic semiconductor laser devices are formed as described in detail later. can get. by this,
It is possible to emit a plurality of laser beams whose emission points are very close to each other, and the directions of linearly polarized light of these laser beams differ depending on the shape of the processed substrate.

Next, the present invention will be explained in detail.

A substrate that has been processed in advance by wet etching or dry etching to form a groove with a depth and width of several tens of micrometres will have multiple planes with different surface indices appearing on the surface. Epitaxial growth (MBE)
When this is carried out, crystal growth occurs parallel to a plurality of planes having different plane indices or preferentially on a specific plane, and several crystal planes are formed. Generally, in MBE, when the growth temperature is low, the diffusion length of atoms adsorbed on the substrate surface is short, so
The crystals grow parallel to the plane of the processed substrate.

For example, the top surface of the substrate before processing faces the (001) plane, and the (00
11) When processed so that the surface appears on the surface, (011)
The amount of flux during film formation on the (001) surface is CO545° to 0.71 times that of the (001) surface, and as a result, the film formation rate is also 0.71 times.

Furthermore, when the growth temperature is high, the diffusion length of atoms adsorbed on the substrate surface becomes long, a plane with a certain plane index determines the growth rate, and some planes appear preferentially.

For example, if a plane is formed on a (001) substrate that is perpendicular to (TIO) and has an angle of 55° to the (001) plane, in the latter half of the film formation on that plane, the (111) plane appears on the surface, creating a flat surface. In this way, in vapor phase epitaxial growth, the growth rate differs depending on the plane index, and the plane with a slow growth rate controls the growth rate, appears as a crystal form on the growth surface, and becomes a stable plane. Such stable surfaces are (100) (411) (111)
Appl, Phys, Let etc. by Sm1th et al.
T, 47(7), P712 (1985).

As you can see from the above, on a pre-processed board,
When the active layer is formed by crystal growth, the thicknesses, etc. of these layers are not necessarily the same for each cut.

In addition, one feature of the present invention is that a quantum well structure is used in the active layer, but in this structure, regardless of whether it is a single quantum well structure or a multiple quantum well structure, the oscillation wavelength depends on the quantum well width. is generally known to change. Therefore, the semiconductor laser device of the present invention can oscillate lasers with different oscillation wavelengths.

Further, the relationship between the photoluminescence emission wavelength λ, its energy ΔEn%, and the quantum well width L2 is expressed by the following equation.

△En=hxC/λ”, (h2/2m”) (rt
・n/L,) ”(n-1, 2, 3...) However, C is the effective mass of the electron or hole, h is the blank constant,
C is the speed of light. That is, as L2 decreases,
The quantum level of electrons rises from the bottom of the electric field or valence band, and the recombination energy increases, so the emission wavelength λ decreases.

For example, when the GaAs well width is 100 people, the photoluminescence emission wavelength at room temperature is 0.84p, and when the well width is 50 people, it is 0.787u. Note that although the wavelength of laser light at room temperature is approximately 0.01 μ larger than the emission wavelength of photoluminescence at room temperature, the above applies as is.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view of a portion of an embodiment of the semiconductor laser device of the present invention.

On the P''-GaAs substrate 21, a p''-GaAs buffer layer 20, a p--A 1xGap-XAs lower cladding layer 19, AI, G
a1-, As lower optical confinement layer 18, quantum well structure active layer (well: A1.aa,-, As, barrier: A1.G
ap-, As) 17, AI, Gap-, As upper optical confinement layer 16, n◆-A
IXGa+-, As upper cladding layer 15, n--GaA
s cap layer 14.5i02 layer 12 is laminated.

Furthermore, P"-, the lower surface of the GaAs substrate 21, 5i02
On the upper surface of the layer 12, a P-side electrode 13 and an N-side electrode 1 are provided.
1 is provided. In addition, there are semiconductor lasers near [I] and [■], and the wavelengths of the laser beams emitted from the active layers with different quantum well widths are different from each other, and the direction of the linearly polarized laser beams is different from each other. The difference is due to the shape of the processed substrate.

Next, a typical manufacturing method of the semiconductor laser device of the present invention will be explained with reference to FIGS. 2(a) to 2(j).

A resist is applied onto the P"-GaAs substrate 21 with the (001) plane facing upward to form a resist film 23. After exposure, a portion of the resist film 23 is peeled off (see FIG. 2).
a)].

Next, by wet etching the substrate 21 on which the resist film 23 is not attached, the substrate 21 and 45 in other parts are etched.
Cut the resist film 2 at an angle of
Remove 3. In this example, the depth of the cut is 30 μm and the width is 60 μm [FIG. 2(b)].

An epitaxial film 24 is formed by MBE [FIG. 2(C)]. As shown in FIG. 1, the epitaxial film 24 includes a P''-GaAs buffer layer 20, p--A1. Gap-XAs cladding layer 1
9, AI, Ga, -, As optical confinement layer 18, quantum well structure active layer (well: Al, Ga, -, As, barrier: Al
y G, a+-y As) 17, AI, Ga,-, As
The optical confinement layer 16, n''-A1.Gap-, As cladding layer 15, and n--GaAs cap layer 14 are laminated in this order.

After forming the epitaxial film 24, a metal mask A125 is deposited, a resist film 26 is formed thereon, and after exposure, etching is performed to remove the resist film in areas other than predetermined portions (FIG. 2(d)).

Using the remaining resist film 26 as a mask, the metal mask A125 other than the predetermined portions is removed by chemical etching, and then the resist film 26 serving as a mask is removed. Next, using ZnAs2, Zn is diffused using a quartz sealed tube method to form a Zn diffusion region 22, and the n shadow region is changed into a P+ type. This Zn diffusion region 22 not only serves as a current confinement, but also causes a decrease in the refractive index due to the disordering of the quantum well structure, making the waveguide type of the semiconductor laser a refractive index waveguide type [Figure 2 (e) ].

After removing the metal mask A125 with acid, a 5i02 layer 12 is formed by CVD [FIG. 2(f)].

A resist is applied on the SiO□ layer 12, and only the portion where the current injection window is to be formed is exposed and removed.The SiO□ layer 12 in the exposed current injection window portion is removed by chemical etching.
Thereafter, the resist is removed (FIG. 2(g)).

Next, an A u /A u -G e layer 11a is deposited, a resist film 27 is formed thereon, and after exposure, unnecessary portions of the resist film 27 are peeled off (FIG. 2(h)).

D. Separate the A u /A u -G e layer 11a by etching to form an n-side type 8i11, and then remove the resist film 27 [FIG. 2(i)].

Cr/Au is deposited on the lower surface of the substrate 21 to form the P-side electrode 13 [FIG. 2(j)]. An oscillator is produced by cleaving the square having the laser structure thus produced in the (TIO) direction, and scribing is performed at the bottom of the V-shaped groove to form a chip. In the embodiment shown in FIG. 1, the substrate temperature during epitaxial film growth is approximately 400° C., which is an example of a low temperature, and the shape of the processed substrate is maintained as it is during growth. Under such conditions, the crystal growth rate is determined by the amount of flux supplied to the surface that has become a surface due to processing, so a semiconductor laser structure can be formed on any surface.

FIG. 3 is a schematic sectional view of a portion of a second embodiment of the invention.

Compared to the example shown in FIG. 1, the 5 processed substrate in the example shown in FIG. It is. In such a case, (001), (114), (111
) faces form the surface. Since the crystal growth rate of these planes is lower than that of other planes, they determine the rate of epitaxial film growth, and as the growth progresses, they gradually exhibit a crystal habit. This makes the active layer flat, so that a high quality active layer with low scattering loss can be obtained. (O
The ratio of the growth rates on the O' 1 ), (114), and (111) planes is approximately 1:0.95:0.90, although it of course changes depending on the growth temperature. To this ratio (001)
When the plane is used as a reference plane, the flux ratio per unit 1fili product due to the inclination of each angle is 1:0.94:
Multiplying by 0.58 gives 1:0.89:0.52.

This is the ratio of growth rates for each surface in FIG. In this way, in MBH, by introducing a certain angle in the direction of flux, [I], [II], [I[+]
In each semiconductor laser in the vicinity, the quantum well width is 1:0.89:0.52, and when the semiconductor laser in the vicinity of [I] is fabricated with a wavelength setting of 0.84 μ, [1
1] is 0.831m for the nearby semiconductor laser, and 0.81p for the semiconductor laser near [m]. In this way, by optimizing the temperature, Ga/As flux ratio, and shape of the processed substrate during MBE film formation, it is possible to adjust the excavation wavelength and the direction of linearly polarized light to fabricate a multi-laser.

FIG. 4 is a schematic sectional view of a portion of a third embodiment of the present invention.

In this example, the substrate is processed in advance so that it is symmetrical, making an angle of 20° or 55° with the (001) substrate, and then the laser structure is fabricated as shown in Figure 2. do. Figure 4 shows (111), (TTI)
This shows the multi-laser when processing is performed so that the surface is exposed. Since the crystal growth rates near [I] and [1] are the same, the quantum well widths are the same and the oscillation wavelengths are the same. However, in this embodiment, since the directions of linearly polarized light are different, the oscillation wavelength is the same, and it can be widely used in applications that require different polarization directions, such as optical heads and laser beam printers.

In all the above examples, the laser structure is the same, but
The present invention is not limited to a specific structure, and as long as the structure has an active layer made of a quantum well structure, the present invention can be applied in various ways in addition to the embodiments described above. be. For example, the material constituting the semiconductor laser is not limited to the GaAs/AlGaAs system described in the example, but also InP/
An InGaAs P system can also be used.

[Effects of the Invention] As explained above, in the present invention, by performing a series of epitaxial growths on a pre-processed substrate, a plurality of films with different surface indices are grown, and active layers with different quantum well widths are grown. As a result, laser beams with different linearly polarized directions and wavelengths can be obtained. Therefore, high precision in hybrid packaging and high technology in conventional manufacturing processes are not required, so yield is improved, productivity is increased, and downsizing can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a part of an embodiment of the semiconductor laser device of the present invention, FIG. 2 is a schematic diagram showing a method of manufacturing the semiconductor laser device of FIG. 1, and FIG. The fourth is a schematic sectional view showing a portion of the third embodiment. 11.-n-side electrode, 11 a...AU/AU-Ge layer, 12."3102 layer, 13."p-side electrode, 14--n--GaAs cap layer 15--n"-AIXGa+ -, As upper cladding layer 16 = A I, Ga, -yAs As upper transparent layer 17
---Quantum well structure active layer (well + A1zGal-ZAs. Barrier: A1.Gap-, As), 18-AI, Gap-yAsAs lower light transparent layer, 19
-P--A1. Ga, -XAs lower cladding layer 20...
・P”-GaAs buffer layer, 21-P”-GaA
s substrate, 22.=Zn diffusion region, 23.26.27... Resist film, 24... Epitaxial film, 25... Metal mask At0

Claims (1)

[Claims] 1) In a semiconductor laser device that oscillates a plurality of laser beams with different linear polarizations, two of the substrates each having a plurality of surfaces with different surface indexes depending on processing.
1. A semiconductor laser device comprising two or more semiconductor lasers each having an active layer formed by vapor phase epitaxial growth stacked on one or more of the surfaces. 2) The active layer has a quantum well structure, and the well width in the active layer in each of the semiconductor lasers is different, and laser beams of different wavelengths are emitted from each of the active layers. The semiconductor laser device according to item 1.