JPS5857773A - Double hetero junction type semiconductor laser - Google Patents

Abstract

PURPOSE:To improve current injection efficiency and enhance optical output by providing a high resistance region at the side of guide passage of a double hetero junction type laser having the flat convex guide passage. CONSTITUTION:The non-additive InP 9 (intrinsic or n<->) is stacked on the plane (100) of the n<+>-InP substrate 1 and the groove is formed in such a depth as reaching the substrate 1 with the width of 2-20mum. Next, the n-Ga0.03In0.97As0.06- P0.94 2 with the forbidden energy band width of 1.3 eV is formed and the upper surface is flattened. Thickness of the layer 2 in the area other than the groove is selected to 0.1-0.6mum. Thereafter, the non-additive GaInAsP (forbidden energy band width 1 eV) 3 and the p-InP 4 are stacked and a laser element can be completed by the conventional methods. According to this structure, since the InP layer 9 having a high specific resistance exists at a side of flat convex guide passage, the current blocking effect can be improved and the current injection coefficient is also improved, thus result in stable lateral mode laser. This laser element thus obtained is resistive to high temperature and high output operation because the sides of guide passage are formed by the stacked wall of the p layer 10 and n-InP layer 9 having the forbidden energy band width narrower than that of the active layer 3.

Description

[Detailed description of the invention] The present invention relates to semiconductor lasers.

One type of semiconductor laser that operates in a stable fundamental transverse mode is a plano-convex waveguide laser, which has a cross-sectional structure as shown in FIG. In this figure, 1+ is an n-type InP substrate, 2 is an nWGaInAsP layer, and 3 is an n-type InP substrate.
Alternatively, it is a p-type GaInAsP layer, which has a smaller band gap than the layer 2. 4 is a P-type InP layer, 5 is an n-type GaInA@P layer, 6 is a striped P-type diffusion region, 7 is a P metal film for the side electrode, and 8 is a metal film for the n-side electrode.

Although this laser is one of the excellent lasers in practical use, the current narrowing effect is insufficient, so there is a current component that does not effectively contribute to laser oscillation. This becomes significant when attempting to increase the optical output by increasing the current density.

An object of the present invention is to provide a plano-convex waveguide semiconductor laser with improved current injection efficiency.

According to the present invention, in a double heterojunction semiconductor laser including a plano-convex waveguide including a plurality of semiconductor layers formed on a medium conductive substrate, a side portion of the plano-convex waveguide is provided. A double heterojunction semiconductor laser is obtained, which is characterized in that a high resistance region is provided in the double heterojunction semiconductor laser.

Next, the present invention will be described in detail according to embodiments using the drawings.

FIG. 2 is a sectional view showing an embodiment of the present invention.

The figure shows laser light (in this specification, the word light is used in the broadest sense, and includes not only visible light but also ultraviolet and infrared light).

) is a sectional view taken in a direction perpendicular to the emission direction. First, the carrier concentration lXl0'', which is doped with 8n, is n+W.
An undoped InP layer 9 is grown to a thickness of about 1.4 μm on the (100) plane of an InP substrate l. The method may be either a vapor phase growth method or a liquid phase growth method. The InP layer 9 is preferably a semi-insulating layer, a substantially intrinsic layer, or a single layer in order to increase the resistivity as much as possible.Furthermore, the InP layer 9 may be formed into a porous layer by controlling the growth conditions; however, the term "porous" It is used to mean that the density is smaller than its original value.

Next, the InP layer 9 is selectively removed to form a groove having a width of 2 to 20 μm and a depth of approximately 1.4 to 1.6 m. It is preferable that the +InP layer 9 not remain at the bottom of the groove, and there is no harm in etching the n-InP substrate 1 a little.
ts-Ga O,03In 0.97As with band gap 1.3 eV at 1xl□)-doped carrier
OJ) 6F0.94 Forming Layer 2 The growth conditions are selected so that the top surface is flat as shown in the figure. Alternatively, the groove may hang downward and be recessed by about 0.1 to 0.3 μm. The thickness is 0.1 to 0.6μ in the flat part other than the groove part.
It is best to set it to about m. Next, undoped GaInAaP
layer (bandgap width 1.0eV)3. The process of forming the P-type InP layer 4 to create a laser is the same as the conventional process, so the explanation will be omitted.

It is clear that with such a configuration, the current constriction effect is improved because the InP layer 9 having a high resistivity is present on the side of the semi-convex waveguide. Moreover, there is basically no difference in the waveguides, and only one additional manufacturing process is required.

FIG. 3 is a sectional view showing another embodiment of the present invention, in which a P-type semiconductor layer 10 is formed to a thickness of about 0.7 μm on a 10n-type InP substrate 1. The semiconductor layer 10 may be InP or may be G-type InAsP with an appropriate band gap. In particular, when the forbidden band width is made smaller than that of the active layer 3, since it also acts as an absorption layer, it absorbs the light leaking through the n-type InP layer and is conveniently set to 0.
Next, an nWInP layer 9 is formed to a thickness of about 0.7 μm, with a thickness of 2 to 20 μm.
? A groove with a width of fi is formed. In this case, the resistivity of the n-type InP layer 9 may not be so large.

The P-type medium conductor layer 10 functions as a current blocking layer. In this case p
Although the npn switching element is parasitic, the presence of the n-type layer 9 is effective in preventing the parasitic effect.

Therefore, it is preferable to keep the diffusion length of minority current carriers in the n771 layer 9 as small as possible. In this respect, it is more effective to make the n-type layer 9 porous.

Qmx Int-xPy whose lattice constant matches InP
The elementary band width of Assy can be varied over a wide range (0.74 to 1.35 eV), and the refractive index is 3.45 (n
(Since it can be varied in the range of 3.65, not only can the waveguide function be the same as the conventional Hx, but also by making the forbidden band width of the PM semiconductor layer 10 smaller than that of the active layer 3. , it can also act as an absorbent layer.

The higher the temperature and the higher the current density, the more likely the parasitic switching effect occurs. Therefore, this embodiment can be said to be more resistant to high temperature operation and high output operation than the case where a pHI is provided at the position of layer 9.

As described above in detail, the present invention is effective in improving the current injection efficiency of a semiconductor laser with stable transverse mode.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional double heterojunction semiconductor laser equipped with a plano-convex waveguide, and FIGS. 2 and 3 are sectional views showing embodiments of the present invention. + 1...n-type InP substrate, 2...n-type Q
aTnAsPI3...n or P-type GaInA
sP layer (active layer), 4...P type InP layer, 5---
−=n-type GaInAsPNI, 6−・−・−, x.

Claims (1)

[Claims] In a double heterojunction semiconductor laser equipped with a plano-convex waveguide including a plurality of semiconductor layers formed on a semiconductor substrate of one conductivity type, a high resistance region is provided on the side of the plano-convex waveguide. A double heterojunction semiconductor laser characterized by: