JPS6014486A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To reduce the oscillation threshold value and to upgrade the external differentiated quantum efficiency by a method wherein three layers, whose conductive types are alternately different from one another, are formed on a substrate having a protrusion in such a way that a layer having either of two ridges standing straight in parallel to each other is formed respectively on both sides of a groove, whose bottom surface comes in contact to the top of the protrusion; and a double hetero structure including an active layer is formed on the semiconductor layers including the ridges. CONSTITUTION:A first current constricting layer 9 of a P type Ga1-xAlxAs and then a second current constricting layer 10 of an N type Ga1-xAlxAs, and furthermore, a third current constricting layer 11 of a P type Ga1-xAlxAs are continuously grown on the surface of an N type GaAs substrate 1, whereon a protrusion has been formed by performing an etching, by a liquid- phase epitaxial method until the surfaces thereof become flat. Two ridges standing straight in parallel to each other are formed on the surface of a wafer, when finished this first-time growth, putting a groove between them by performing an etching. An N type Ga1-xAlxAs clad layer 2 of the first layer, a non-dopped Ga1-yAlyAs active layer 3 of the second layer, a P type Ga1-xAlxAs clad layer 4 of the third layer and a P type GaAs electrode forming layer 5 of the fourth layer are continuously grown on the surface of the substrate 1, whereon the two ridges have been formed, by a liquid-phase epitaxial method again.

Description

[Detailed Description of the Invention] [Object of the Invention] The present invention is based on TRF3 (Twin RitLge5ubz), which has already been developed by the present inventors.
The present invention relates to an improvement of a semiconductor laser device having a trate) structure. In recent years, there has been an increasing demand for high-power semiconductor laser devices that emit fundamental transverse mode oscillation in a wide range of fields, such as for writing optical disk files and laser printers, and the TR8 type semiconductor laser device meets this demand. .

FIG. 1 shows a conventional TR8 type semiconductor laser device using a square substrate, in which two glue holes are formed vertically in parallel on a substrate 1, and each layer 2. 4.5 is continuously grown, and zinc is diffused from the crystal surface for current injection.
After this, electrodes 6.7 are formed on both the upper and lower surfaces. Because this structure is suppressed due to the anisotropy of crystal growth, the growth on the ridge is suppressed compared to the side surface of the ridge, so i1'2 on the ridge:
The light that forms the extremely thin active layer with good reproducibility largely seeps into the cladding layer, and the light that seeps into the first cladding layer 2 is absorbed by the substrate on the grooves other than the grooves, so it is confined in the grooves between the ridges. This results in stable fundamental transverse mode oscillation.

However, the conventional structure shown in FIG. 1 has the following problems. (1) The current injected from the zinc diffusion region 8 flows not only to the groove where oscillation occurs but also to the grooves other than the groove, so these currents do not become losses but are effective currents to the groove. injection. (2)
Since there is a limit to the controllability of thermally diffusing zinc in the form of stripes to an arbitrary depth with good reproducibility, there is a possibility that the diffusion front will not reach the fifth cladding N4.
Alternatively, it may reach the active layer 5, which causes a decrease in the oscillation rate. An object of the present invention is to provide a TR8 type semiconductor laser device having a novel structure in which these problems are solved.

[Structure of the Invention] The semiconductor laser device of the present invention is provided by alternating conductivity types so that a layer having grooves standing upright in parallel on both sides of a groove whose bottom surface is in contact with the top of the protrusion is formed on a semiconductor substrate having a protrusion. At least one layer is formed that differs from 1 to 1.
A double heterostructure including an active layer is formed on the semiconductor layer including the two glue holes.

The structure of the present invention will be explained with reference to FIGS. 2 and 6. Etched the surface of the n-arm GαAs substrate 1 (Fig. 6 α) on which protrusions with a height of 2.2 μm and 3 μm were formed using a liquid phase epitaxial method.
The first current confinement layer 9 is placed on the protrusion to a thickness of 02 μm, then n
Similarly, the second current confinement layer 10 of type 0a1-:t, 711χA is formed on the protrusion to a thickness of □2 μm, and further P7fiGc
L1-xllxAz tD 573t Mf, Continuously grow the narrowing layer 11 until the surface becomes flat (fifth tob). The first growth of ζ has been completed.

On the surface of the Ever, two parallel ridges with a height of 15 μnL and a width of 20 μm in the <011> direction are formed by etching, sandwiching a 4 μm wide door groove. The groove between the ridges is located directly above the protrusion and reaches the bottom of the FiL type substrate 1. On the other hand, the flat part on the outside of the ridge remains in the third position even after etching.
The current narrowing layer 11 remains (Fig. 6C). On the surface of the substrate 1 with the ridge formed in this way, a first layer of n-type Gα1-xALxy cladding layer 2 is formed again by the liquid phase epitaxial method so that the thickness above the ridge is approximately Q, 21 tms, and the second layer is non-doped Gα1-yAZ yAz. The active layer 3 is also approximately 0.05 μm thick, the third layer P type □a1-xllxAz cladding layer 4 is approximately 1.5 μm thick, and the fourth layer is P type GaA.
Similarly, the s-electrode type sensitive layers 5 are continuously grown to a thickness of about 0.5 μm (FIG. 6d). In addition, in the above example! =0. -45, y = 0.08. A P-side electrode metal is vapor-deposited on the fourth electrode forming layer 5 and alloyed to form a P-side ohmic electrode 6. A roadside electrode metal is thinly deposited on the substrate side and alloyed. After forming the ohmic electrode 7 on the side, the semiconductor wafer of the present invention shown in FIG. 2 is replaced.

[Effects of the Invention] Since the semiconductor laser device of the present invention has the above structure, it has the following effects. (1) First
The fc current narrowing layer formed during the second epitaxial growth puts the Pn junction in a reverse bias state and blocks current flow. Therefore, the current injected from the growth surface is intensively injected into the active layer above the groove where oscillation occurs. As a result, the oscillation threshold can be lowered and the external differential quantum efficiency can be improved. As a result of experiments, the oscillation threshold is approx.
+077LA, external differential S, and particle efficiency were approximately 70 factors, and it was confirmed that the laser diode had a lower threshold value and higher efficiency than the conformal 0TR8 type semiconductor laser. (2) 1
[The current narrowing layer formed by the gi-th epitaxial growth is formed by protrusions previously formed on the substrate into a shape with skirts on both sides of the protrusions, as shown in FIG.

Therefore, since the depth of the vortex between the ridges and the height of the step outside the ridge 111j can be made the same by appropriately determining the height of the protrusion and the width of the ridge, this can be done in one etching.

(3) In the structure of the present invention, the passage of current is limited to the groove between the rich, so there is no need for zinc diffusion for current injection, which is required in conventional TR8 semiconductor lasers, so the depth of zinc diffusion can be reduced. This eliminates a decrease in the oscillation rate due to variations in the oscillation rate, and also greatly simplifies the process after epitaxial growth.

Although the present invention has been described above using a L-type substrate, the present invention can also be implemented in the same manner using a P-type substrate, and the same effects can be obtained.

[Brief explanation of drawings]

FIG. 1: A cross-sectional view of a conventional TR8 type semiconductor laser device. FIG. 2: A cross-sectional view of a TR8 type semiconductive laser device of the present invention. FIG. 3: A manufacturing process diagram of a TR8 type semiconductor laser package of the present invention. α, b, c, and d indicate each step. 1--n type □aAs substrate, 2- n type Gc1-xll
xAs l rad layer, 6... non-doped Gαi -3
1AZ yhs active layer, 4...P-type Gα1-x)Ax
Ag cladding layer, 5... Le-type GaAz electrode forming layer, 6
... P-type ohmic electrode, 7... Le-type ohmic electrode, 8... Zinc diffusion region, 9 - P-type Ga 1-x
ALxAt first current narrowing layer 10-n, fJ, Gl
-xlLx)s 2nd current narrowing layer i i-:p type Gα1-
xAlxAI 3rd current narrow layer fang 1 figure 2 figure 3 figure + 4)

Claims (1)

[Scope of Claims] At least one layer having conductivity types that is alternately different so that a layer having grooves standing upright in parallel on both sides of a groove whose bottom surface is in contact with the top of the projection is formed on a semiconductor substrate having a projection. One layer is formed. A semiconductor laser device characterized in that a double heterostructure including an active layer is formed on the semiconductor layer including the two glue holes.