JPS59130492A - Semiconductor laser device and manufacture thereof - Google Patents

Abstract

PURPOSE:To contrive the stabilization of high output and transverse mode by a method wherein the first and fourth semiconductor layers are set smaller than the second and third semiconductor layers in refractive indices, and the refractive index of the third semiconductor layer is set larger than that of the second semiconductor layer, and the first and forth semiconducltors are so provided as to have conductivity types reverse to those of each, then, the forbidden band widths of the second and forth semiconductor layers are so set as to be larger than that of the third semiconductor layer at the same time. CONSTITUTION:A mesa stripe 12 is formed. At this time, mesa depth is made to reach a GaAs substrate in order to facilitate a burial growth thereafter. An active layer 4 exposed to the side surface of the stripe by selective etching is removed with H3PO4 series etchant, thus forming a cross-sectional structure. Next, the mesa stripe is filled with a P-Ga0.55Al0.45As layer 7 and an N-Ga0.55Al0.45As layer 8 by liquid epitaxial growth, and the selective diffusion 9 or entire surface diffusion of Zn is performed, afterwards ohmic electrodes 10 and 11 are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to the structure of a high-output semiconductor laser device and its manufacturing method.

[Prior art]

Many proposals have been made to try to increase the output of semiconductor laser devices. Typical examples include providing a so-called optical guide layer in contact with the active layer and making the output end face of the laser beam transparent, but it cannot be said that a sufficiently high output has been achieved yet.

[Purpose of the invention]

An object of the present invention is to provide a high output semiconductor laser device.

Another object of the present invention is to provide a semiconductor laser device with high output and stabilized transverse mode.

Still another object of the present invention is to provide a structure of a semiconductor laser device that is easy to manufacture and a method of manufacturing the same.

[Summary of the invention]

A first layer is formed on a predetermined semiconductor substrate. Second. 3rd and 4th
The first and fourth semiconductor layers have at least a light trapping region in which the semiconductor layers of
The refractive index of the third semiconductor layer is smaller than that of the second semiconductor layer, and the refractive index of the third semiconductor layer is set to be smaller than that of the second semiconductor layer. At least the first and fourth semiconductor layers are provided to have opposite conductivity types. 2nd and 4th at the same time
The forbidden band width of the semiconductor layer is set to be at least wider than that of the third semiconductor layer. Thus, carriers are confined to the third semiconductor layer, while photons are confined to the second and third semiconductor layers. The second semiconductor layer is commonly called a light guide layer, the third semiconductor layer is called an active layer, and the first and fourth semiconductor layers are called cladding layers. In a specific semiconductor laser device, a semiconductor layer is further provided between the substrate and the optical confinement region or above the optical confinement region, but the present invention can also be applied in this case, and the essence of the present invention is There is no effect on

In the present invention, the width of the second semiconductor layer in a cross section perpendicular to the traveling direction of the laser beam and in the direction parallel to the pn junction surface is wider than that of the third semiconductor layer, and at least the first to The fourth semiconductor layer has a mesa stripe shape, and the sidewall of the mesa stripe semiconductor layer in a direction perpendicular to the traveling direction of the laser beam is embedded with a fifth semiconductor layer. Fifth
The refractive index of the semiconductor layer is made smaller than the refractive index of at least the second and third semiconductor layers. In this case, it is preferable for manufacturing reasons that the buried layer reach the semiconductor substrate. Further, the fifth semiconductor layer may be composed of multiple layers.

Since the width of the light guide layer is wider than that of the active layer, higher output can be achieved than by providing a light guide layer.

Furthermore, it is more preferable that the active layer does not reach the output end face even in the cross-sectional structure in a plane parallel to the direction of propagation of the laser beam, while the light guide layer reaches the output end face.

Since the active layer is covered with a buried layer, light is mainly emitted from the light guide layer to the outside, making it suitable for mountain climbing.
It is also advantageous in extending the lifespan.

Note that the stacking order of the mantle light confinement region composed of the stacked layers of the "th" to "fourth" semiconductor layers may be stacked in the reverse order to the above-mentioned order for the substrate.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

Example 1 FIG. 1 is a cross-sectional view sequentially showing the manufacturing steps of a semiconductor laser device of the present invention. Note that each figure is a cross-sectional view taken on a plane perpendicular to the laser beam. As shown in Figure 1(a), n-Q
n on the aAS substrate 1 by liquid phase epitaxial growth method.
-Qa O,55AL6,45 A s clad Jfl
i (thickness 0.8-2 μm) 2 , n-Gao,
t4Ala, 26As light guide layer (thickness 0.4-3 μm
) 3, undoped G"o, 5aAto, t4As active layer (thickness 0.04-0.4 μm) 4, I) -Gao,s
s AAo4sA s cladding layer (thickness 0.8 to 2 μm
) 5, and I) -Ga o, 5Ato, 2As cap layer (thickness 0.5-1 μm) 6 are sequentially grown.

A GaAs layer is normally used as the cap layer, and it may be used, but in this example, Qao, BA7O was used for the purpose of not epitaxially growing on the mesa stripe during buried growth and to make ohmic contact as easy as possible. , 2AS layer. Next, a mesa stripe 12 is formed as shown in FIG.
Let it reach the As substrate.

SBH structure (Strip Buried 1-iete
rostructure), it is necessary that the width of the optical guide layer is wider than the width of the active layer in the direction perpendicular to the stripes, and in this example, selective etching is performed as shown in FIG. 1(C). and pQa o, 5sA
Only the ground layer (2, 5) was etched by about 1 μm from both sides. Here, HF was selectively used as the tucking liquid. After that, the active layer 4 exposed on the side surface of the stripe by this selective etching is etched with HaP.
It was removed using a 04 series etchant to form a cross-sectional structure as shown in FIG. 1(d). Next, I)-Gao, 5sA7o4sAs layers 7 and 1 were formed by liquid phase epitaxial growth.
The mesa stripe was filled with l-Gao, 5sA, 70.4sAs layer 8 (FIG. 1(e)). In this example, the outside of the stripe region is reverse biased, so current flows only in the stripe region. Of course, in the case of a laser having an SBH structure, this buried layer may not be divided into two layers, but may be buried in one layer. Furthermore, the buried layer may be configured as a multilayer structure. Also, this buried layer is Qa O, 55AA
A high-resistance layer made of 0, 45AS, etc. may also be used. FIG. 1(f) is a final cross-sectional view of the device. After Zn is selectively diffused 9 or entirely diffused by a well-known method, ohmic electrodes 10 and 11 are formed. The reflective surface of the resonator was formed by cleaving the crystal.

According to this example, since the mesa depth reaches the substrate, buried growth is easy even if the AtAS concentration of the light guide layer (Ga5-xAtXAs) is high (for example, X=0.26), An SBH structure can be formed even if the wave wavelength is in the visible range. In fact, in this example, the oscillation wavelength is 7
A stable device with a single transverse mode was obtained up to 80 nm and 50 mW. Compared to visible semiconductor lasers that have been reported so far, the transverse mode is stable up to an output that is about 3 to 5 times higher, and this is an extremely excellent device characteristic.

Example 2 FIG. 2 shows the above semiconductor laser device of Example 1,
This figure shows a cross-sectional structure in a direction parallel to the laser optical axis of an element whose end face is made transparent to laser light. In the figure, the same reference numerals as in FIG. 1 indicate the same parts. The light guide layer 3 exists up to the laser beam reflecting end face, while the active layer 4
The end face is located inside the reflecting end face. The manufacturing process is shown in FIG. 1(d). After forming the mesa stripe 12, 1) Ga of the light emitting output end face is formed.
o, 5Ato, 2A s cap layer 6, pGao, 5s
Only the Ato4sAs cladding layer 5 and active layer 4 are removed by selective etching. Thereafter, the outside of the stripe was filled with a GaAtAs layer in the same way as the buried growth in Example 1.

Note that other steps and the like are the same as in Example 1.

According to this example, a visible semiconductor laser device with an oscillation wavelength of 7800 m, a single transverse mode up to 50 mW, and a maximum optical output IW was obtained.

〔Effect of the invention〕

According to the present invention, it is possible to form an 8BH structure even in a visible semiconductor laser. As a result, the oscillation wavelength was 780 n
A device with stable transverse moat up to m, 5-Q, mW was obtained.

In addition to the above characteristics, the maximum light output I
A W element was obtained, and it can be seen that the present invention is effective in increasing the output and stabilizing the transverse mode at high output.

The present invention applies not only to the compositions shown in the examples, but also to each Ga□
-x A t Furthermore, a p-type substrate having a conductivity type opposite to that of this embodiment may be used, and in this case, it is only necessary to change the conductivity type of the epitaxial layer to the conductivity type opposite to that of this embodiment.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the device showing the manufacturing process of the laser device according to the present invention, and FIG. 2 is a cross-sectional view of the device showing another embodiment of the present invention. FIG. 1--n-Q aAs substrate, 2- n-Gao, 5
sAto, 4sAs cladding layer, 3-n-Ga c7
4A7o, 26A s optical guide layer, 4... Undoped Gao8s A/Lo, 14A s active layer, 5
- p-Qa 0.55 kto4s AS cladding layer,
6-1) -Ga04Ato, 2AS cap layer, 7-
p-Gao, 5sA7o, 4sAs layer, 8-n-Ga
o, 5sAto, 45As layer, 9-Z n diffusion layer, 10
...n ohmic electrode, 11...p ohmic electrode. ■ 1 Figure (a-)
(1))2 □□■ (e>
(4) Figure 2

Claims (1)

[Claims] 1. A first . Second. The third semiconductor layer has at least a light trapping region in which the third and fourth semiconductor layers are in contact with each other, the first and fourth semiconductor layers have a smaller refractive index than the second and third semiconductor layers, and the third semiconductor layer has a smaller refractive index than the second and third semiconductor layers. The refractive index of the layer is greater than that of the second semiconductor layer, and
and the forbidden band width of the fourth semiconductor layer is larger than that of the third semiconductor layer, and at least the first and fourth semiconductor layers are provided so as to have mutually opposite conductivity types;
The light confinement region is configured in a mesa stripe shape, and the sidewalls of the mesa stripes are embedded with a fifth semiconductor layer, and the cross section perpendicular to the traveling direction of the laser beam is formed with a bonding surface existing within the light confinement region. A semiconductor laser device characterized in that the width of the second semiconductor layer in the parallel direction is wider than that of the third semiconductor layer. 2. Claims characterized in that the end of the second semiconductor layer exists up to the reflective end face of the laser resonator, and the end of the first semiconductor layer exists inside the reflective face as well. The semiconductor laser device according to item 1. 3. At least the first . the step of laminating second, third and fourth semiconductor layers, wherein the first and fourth semiconductor layers have a smaller refractive index than the second and third semiconductor layers; The refractive index is larger than that of the second semiconductor layer, and the forbidden band width of the second and fourth semiconductor layers is larger than that of the third semiconductor layer, and at least the first and fourth semiconductor layers are The first and fourth semiconductor layers are selectively removed, and the first and fourth semiconductor layers are selectively removed, and the laminated semiconductor layers are selected to have opposite conductivity types and have a depth that reaches the semiconductor substrate. a step of reducing the width in a cross section perpendicular to the direction of travel and parallel to the bonding surface existing in the light confinement region; a step of selectively removing the 30th cow conductor layer; A method of manufacturing a semiconductor laser device, comprising the step of forming a fifth semiconductor layer. 4. Before forming the fifth semiconductor layer on the sidewall of the mesa stripe, at least the output ends of the fourth and third semiconductor layers in the traveling direction of the laser beam