JPS606118B2 - semiconductor laser equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor laser device capable of continuous oscillation in a low-order mode at room temperature and under low current.

An injection type semiconductor laser using a pn junction has a semiconductor layer with a forbidden band width 4 mm wider than the above semiconductor layer and a larger refractive index at the junction interface, so that carriers injected for recombination radiation and It is possible to improve the confinement effect of emitted light and realize an improvement in gain.

For example, a Ga trillion-(Ga.AI) AS double heterostructure semiconductor laser fully satisfies the above conditions,
In addition, since the physical properties such as crystal lattice constants and thermal expansion coefficients match well, continuous oscillation is currently possible at room temperature and under low current. Conventional GaAs-(Ca・AI)As
An example of a double heterostructure semiconductor laser device is shown in FIG. n-type (GaOAI) on n-type GaAs substrate crystal 1
Mother layer 2, GaAs layer or (Ga.As) which becomes the active region
As layer 3, p-type (Ga/AI) As layer 4, a p-type Ga pseudo layer 5 is grown in order to make it easier to form an ohmic electrode,
After forming the Sio2 film 6 on the growth surface by chemical vapor deposition, a band-shaped conductive region 9 smaller than the spot size is formed in a part of the Sio2 film 6.
The ohmic electrode 8 is attached. The feature of the semiconductor laser device shown in FIG. 1 is that the threshold current density of laser oscillation can be reduced by providing a band-shaped current-carrying region 9 smaller than the spot size. When the thickness of the active region 3 was set to 0.4 m, continuous oscillation at room temperature was possible with a value current density of about 2.1 KA/m. However, the semiconductor laser device structure shown in Fig. In this case, since a band-shaped current-carrying region relying on the metal electrode holes is formed only at one end of the element, it is difficult to avoid the spread of the current, and if the width of the band-shaped current-carrying region 9 is narrowed, the increase in the threshold current density becomes significant, and at room temperature. Continuous oscillation is also impossible.

For this reason, it has been difficult to reduce the order of the lateral mode during Caesar oscillation. Furthermore, when attempting continuous oscillation for a long time at room temperature, the above result shows that the current-carrying region becomes wider and the operating current for laser oscillation becomes larger. The purpose of the present invention is to ``Considering the above-mentioned problems, even if the width of the band-shaped current-carrying region is narrowed,'' it is possible to reduce the value current density and at the same time enable continuous oscillation at room temperature. )
An object of the present invention is to provide a semiconductor laser device that oscillates a laser beam.

The gist of the present invention is to use a p-conductivity type semiconductor substrate crystal, and to have a high resistance layer or a semiconductor region forming a pn junction with the semiconductor substrate crystal at the interface with the semiconductor layer adjacent to the semiconductor substrate crystal, as described above. The purpose of the present invention is to provide a band-shaped current-carrying region in a part of the high-resistance layer or the semiconductor region.

In a semiconductor laser having a double heterostructure, by using a p conductivity type semiconductor substrate crystal and providing a current constriction means in the semiconductor region on the p conductivity type region side, it is possible to sufficiently ensure current constriction ability, Therefore, even if the width of the band-shaped current-carrying region is narrowed, it is possible to minimize the increase in current density.

According to the present invention, the advantage of internal current constriction in that the active layer can be brought close to the internal current constriction means can be fully exhibited. Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 2 shows an embodiment of a semiconductor laser device according to the present invention. Due to crystal growth problems, GaAs-
(Ga・AI)As-based double heterostructure element was created, but it is made of p-type Ga with mirror polished (100) plane.
A high-resistance layer 12 is formed on the As substrate crystal 11 by proton irradiation, leaving only a portion where a current-carrying region 13 with a desired width in the [110] direction will be formed. As a crystal, after lightly etching the wafer surface with a 4:1:1 (volume ratio) mixed solution of 2S04/202/uniform system, p-type No. 3G was also etched using a continuous liquid phase epitaxial method.7As layer 4 , Vandove Ga vessel layer 3, n-type Mo.30 body.7As layer 2 "n-type G
The aAs angle 0 is grown sequentially.

Subsequently, on the surface of the epitaxial wafer that has finished growing, only the part where the band-shaped current-carrying region 5 is to be formed is left at a position that is the same width as the band-shaped current-carrying region 13 and completely overlaps with it, and the other parts are formed using a Zn diffusion method. Katayama o. 3G too. A p-type semiconductor layer is formed up to a part of the 7As layer 2.

After that, 7 p-type GaAs ohmic electrodes were formed, followed by an n-type GaAs ohmic electrode 8.
The characteristics of the device thus obtained are as follows: The width of the band-shaped current-carrying region is 40 mm.
French m, 20 French m "loAm" When the thickness of the active region 3 is 0.4 mm at 5 French m, the laser oscillation at room temperature is
The value current density is 1. Hina A no To 1. Song A no Carp, 2.
Dislike plate A, and 2. Continuous CW oscillation was possible in all cases with shoe A. Fig. 3 shows the relationship between the width of the band-shaped conductive region, the laser oscillation, and the value current density of the conventional semiconductor laser device and the semiconductor laser device according to the present invention. As shown by the curve No. 32, the device according to the present invention tends to oscillate in contrast to the conventional device even though the width of the band-shaped current-carrying region becomes narrower.
It can be seen that the increase in value current density is significantly smaller. Sariko ~ For those with band-shaped energized area width of 10 m and 5 Am ~
Single lateral mode during laser oscillation (Kotoji mode)
can be obtained with good reproducibility. Furthermore, in the comparative example shown in FIG. 3, the conventional semiconductor laser device has the structure shown in FIG. 3, and the semiconductor laser device according to the present invention has the structure shown in FIG. It is.

As shown in this example, by using a p-conductivity type semiconductor substrate and configuring a band-shaped current-carrying region using a high-resistance layer, even if the width of the band-shaped current-carrying region is narrowed, the current density and current density are low. The increase in current density has been suppressed to a minimum while ensuring that the current density increases.By using a p-conductivity type semiconductor substrate, the cladding layer provided on top of this substrate must naturally be of p-conductivity type. , there is no risk of problems such as crystallinity deterioration due to dopants in the cladding layer.The present invention has been explained in detail above, but these are only examples of the present invention, and the high resistance layer is formed by the epitaxial method. However, the same excellent results as above can be obtained.

Furthermore, the same excellent results as described above can be obtained even if a semiconductor layer forming a pn junction with the substrate crystal is provided instead of the high-resistance layer and the band-shaped current-carrying region 15 is formed by a known technique.
In this example, p conductivity type G is used in the same machine as in the previous examples.
When a false substrate is used, an n-conductivity type semiconductor layer is provided adjacent to this p-conductivity type Ga carrier substrate, and a band-shaped conductive region is formed in this semiconductor layer, the following advantages occur.

Compared to the case where a band-shaped current-carrying region is formed using an n-conductivity type semiconductor substrate and a p-conductivity type semiconductor layer, the effect of suppressing the spread of current by selecting the conductivity type as in this example is extremely sufficient. It can be done.

This is because the semiconductor layer for forming the band-shaped current-carrying region in this example is an n-conductivity type layer, so even if the n-conductivity type layer absorbs the laser light generated in the active layer, the electrons and holes generated in this layer are Against China
Since holes, which are minority carriers, have a short diffusion length, they recombine before they diffuse into the layers on both sides. Therefore, “
No accumulation of majority carriers occurs. Therefore, in this example, the current limiting function of the band-shaped current-carrying area can be fully fulfilled. On the other hand, when a band-shaped conductive region is formed using a p-conductivity type semiconductor layer, the minority carriers in the semiconductor layer are electrons.Since these have a longer diffusion length than holes, the L-minority carriers spread through the layers on both sides. This causes accumulation of majority carriers.For this reason, the barrier provided to block carriers is lowered, and the current limiting function of the band-shaped current-carrying region is significantly reduced.As described above, the semiconductor of this example According to the laser device, even if the width of the current-carrying region is narrowed, it is possible to solve the problem of decrease in efficiency due to current spread, absorption loss of coupled radiation light, etc., and it is also possible to lower the order of the transverse mode.

As explained above, the present invention relates to GaAs-(Ga.N)
In addition to ship-type double heterostructure semiconductor laser devices, the active region has a relatively large forbidden band width narrowed by semiconductor layers of different conductivity with a relatively large forbidden band width and a relatively small refractive index. Even in any injection type semiconductor laser device having a structure in which a small semiconductor layer with a relatively high refractive index is interposed, if the width of the band-shaped conductive region is narrowed, continuous oscillation at a low current at room temperature is possible. This has a great effect on improving the optical characteristics of semiconductor lasers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a perspective view of an example of a conventional GaAs-(Ga.yama)As-based double heterostructure semiconductor laser device.

FIG. 2 shows a perspective view of an embodiment of a GaAs-(Ga.N) vessel-based double heterostructure semiconductor laser device according to the present invention. FIG. 3 is a curve diagram showing the relationship between the band-shaped current-carrying region width, laser oscillation, and value current density of a semiconductor laser device with a conventional structure and a semiconductor laser device according to the present invention. This is shown in . Turtle...n
type Ga$ substrate crystal, 2...n type (GaOAI) layer, 3.
... undoped GaAs layer which becomes the active region, 4...p type (
Ga/M)As layer, 5...p-type GaAs layer, 6...Sjo2 film for forming a band-shaped current-carrying region, 7...p-type Ga pseudo-ohmic electrode L 8...p-type GaAs ohmic electrode, 9, 13, 1
5... Band-shaped current-carrying region "io... N-type Ga carrier layer, turtle 1... p-type Ga carrier substrate crystal, turtle 2... high-resistance layer, 1 4... Zn diffusion layer (p-type semiconductor layer), 31, 32.・.

Strip current carrying area width and squeegee value. Tsutomu diagram hair z diagram Many 3 figures

Claims (1)

[Scope of Claims] 1. A semiconductor substrate having at least a first cladding layer, an active layer, and a second cladding layer above the crystal, a laser beam feedback means, a means for injecting current into the active layer in a band shape, and It has at least a high resistance layer at the interface with the semiconductor layer adjacent to the semiconductor substrate crystal, and a part of the high resistance layer is energized in a band shape in the traveling direction of the laser beam corresponding to the band-shaped energization area of the current injection means. A semiconductor laser device having a structure in which regions are formed, wherein the semiconductor base crystal is of p conductivity type, the first cladding layer is of p conductivity type, and the second cladding layer is of n conductivity type.
A semiconductor laser device characterized by being of a conductive type. 2. At least a first cladding layer, an active layer, and a second cladding layer above the semiconductor substrate crystal, and a laser beam feedback means, a means for injecting current into the active layer in a band shape, and a layer adjacent to the semiconductor substrate crystal. at least a semiconductor region forming a pn junction with the semiconductor substrate crystal at the interface with the semiconductor layer, and a part of the semiconductor region has a conductive region extending in the direction of propagation of the laser beam corresponding to the band-shaped current-carrying region of the current injection means. A semiconductor laser device having a configuration having a band-shaped conductive region, wherein a forbidden band width of the semiconductor region forming a pn junction with a semiconductor substrate crystal is smaller than a forbidden band width of the active layer, and the semiconductor substrate crystal is of p-conductivity type. . A semiconductor laser device, wherein the first cladding layer is of a p-conductivity type, the second cladding layer is of an n-conductivity type, and the semiconductor region forming a pn junction with a semiconductor substrate crystal is of an n-conductivity type.