JPS6077485A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To enable to stably oscillate with a low threshold value current by doping an impurity having deep impurity level in a current blocking layer to shorten the lifetime of the minority carrier. CONSTITUTION:A P type GaAs current blocking layer 2a dopes the prescribed density of impurity having deep impurity level to shorten the lifetime of the minority carrier. Electrons in the section corresponding to the layer 2a are collected once to the deep impurity level Ed, and the electrons and the holes are recombined. Therefore, they are recombined in a very short time as compared with the recombination of the electrons of direct transmission band and the holes of valency electron band. Accordingly, the lifetime of the minority carrier can be remarkably shortened by doping the impurity having the deep impurity level. Thus, the current blocking capacity is increased to reliably perform a current constriction operation, and stable oscillation can be performed with low threshold value current.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technology of the Invention] The present invention relates to a semiconductor laser device, and more particularly to an improvement for improving the current blocking effect of a current blocking layer of an internal current confinement type semiconductor laser device.

[Prior art]

In a semiconductor laser device, in order to oscillate in a stable transverse mode and at a low threshold, the active layer must have some sort of refractive index guide mechanism and a sufficiently narrow, for example 5μ
A current confinement structure from the IDJ is required so that the current flows in a concentrated manner in a striped region having a width of about m or less. As such a current confinement structure, zinc (Zn) is injected from outside the crystal.
), etc., to concentrate the current by diffusing the
There are two methods: a method in which a current blocking layer is built inside the crystal and a method in which the current is concentrated by providing striped openings in the blocking layer.

FIG. 1 is a perspective view showing the structure of a conventional internal stripe type semiconductor laser device incorporating a current confinement structure based on the latter method. In FIG. 1, (1) is n-type gallium arsenide (GaAsAZxGaH-) which is the first conductivity type and is doped with silicon (Sl).
xA 8 ) cladding layer, (4) is n-type AtyGa,
-yp, ts active layer, --- (51G map) Cedar Atx
GaAs clad hI7, (6) is p-type GaAe contact (1-x electrode mounting) Ii'i 1 (71ki p-side electrode, (
81 is an n-side electrode, and (9) is a narrow A-striped opening provided in the p-type current blocking layer (2). And n
The WJ (31 is in contact with the substrate ill through this opening).

In this structure, the p-side electrode (7) is positive, and the n-side electrode - (
When a negative polarity voltage is applied to 8), a p-n junction between the p-type current blocking layer (2) and the n-type rad layer (3) or the opposite occurs in the region other than the opening (9). Since it becomes a bias, no current flows, and the electric current v1j flows concentrated only in the Dil IJ section (9). Therefore, electrons and holes are injected into the part of the active layer (4) corresponding to this part, and due to their recombination, light is emitted by recombination in the part of the active layer (4) near the striped opening (9). or occur. Then, if the injection level is sufficiently increased and RIG U7 discharge begins, laser excavation should eventually occur.

However, such a p-type LJaAs current blocking layer (2)
In the structure using the p-type +]aAθ current blocking # (
More active than the energy gap of 21, KY't +4
Since the energy gap is smaller than the energy gap of 1, the active layer (4)
Due to the light generated, electron-hole pairs are generated in the current block B'l12). In Figure 1, electrons are shown as black circles, and genuine cards are shown as white circles. Then, electrons, which are minority carriers, move to the n-shaped rad layer (3) and the substrate f1) by diffusion, and holes, which are majority carriers, accumulate in this current stopper layer (2). As a result, the potential barrier of the current blocking fff+2+ is lowered, making it impossible to obtain a sufficient current blocking effect, and a so-called turn-on phenomenon occurs in which current flows even outside the striped opening (9). Because current leakage occurs in this way, the current blocking layer 1 must be too thick.
Unless 2) is used, it is difficult to obtain a semiconductor laser device that stably oscillates at a low threshold value.

[Summary of the invention]

This invention was made in view of the above points, and by doping an impurity with a deep impurity level into the current blocking layer, shortening the lifetime of minority carriers and shortening the diffusion length, sufficient The present invention provides a semiconductor laser device that has current blocking ability and stably oscillates at a low threshold.

[Embodiments of the invention]

FIG. 2 is a perspective view showing the structure of one embodiment of the present invention. In the figure, (2a) is a p-type doped with impurities having a deep impurity level to a predetermined degree to shorten the lifetime of minority carriers.
This is a GaAs type current blocking layer, and the other structure is exactly the same as the conventional example shown in FIG.

Figure 3 shows the energy in the part along the X-Y line where the opening (9) is not provided in Figure 2 when a voltage is applied to forward bias the active layer (4). In the band diagram, the symbols i11 to (6) represent the hunt end of the energy, and E represents the Fermi'bel. In general, chromium (c,), cobalt (Co), iron (F
.

), metals such as nickel (N1) are GaAs l ”x
It is well known that impurity levels form deep in the energy cap E of crystals such as GaI-"Yokachi. For example, tellurium (T, ), which is well known as type 11 impurity, is 0.0. Whereas C, has an impurity level at a very shallow level below 0.003 eV.

is O,'70 eV above the valence band, that is, the bandgap of Gal+ is about 1.4. It has an impurity level at a deep level of approximately medium eV. on such a deep impurity level.

Electrons and holes recombine rapidly through the .

That is, as shown by the arrow in the part corresponding to the current blocking Itfj (2a) in FIG.
Since the child and the positive plate (indicated by white circles) recombine, the recombination occurs between II'1, which is much shorter than the direct recombination of electrons in the conduction band with holes in the valence band. Therefore, by doping with an impurity having a deep impurity level, the lifetime of minority carriers, that is, the lifetime of electrons in this embodiment, can be greatly determined. And the lifetime τ of the electron. If the deviation is small, the expansion length "n - r (where 1) n is the electron diffusion constant) can also be made small.

Therefore, in this example, n-type htyGa1-yA
Even if the light generated in the s-active layer (3) reaches the p-type GaA3 iL current blocking layer 2) and generates 1 to-hole pair, the 2-in-time τ in the current blocking layer (2). is very small, so I++ will combine in a short time, and if the thickness of the - mud blocking layer (2) is made thicker than the electron diffusion length JJn, the electrons will become semi-exclusive J on the 1lltl side due to diffusion. It never moves.

Therefore, the conventional problem that holes are trapped in the current blocking layer (2), the potential barrier is lowered, a turn-on phenomenon occurs, and the current confinement effect is lowered can be overcome.

Note that the doping amount of C1 added to the p-type GaAs current blocking layer (21) is 1X when a normal liquid phase growth method is used.
A concentration of about 10/am can be achieved relatively easily. Also, although it depends on the carrier concentration of the current blocking layer (2), the concentration of Cr is l×1014/Cm3 to 1×1017
/Cm3 can be used.

In the above embodiment, an n-type as the first conductivity type and a p-type as the second conductivity type have been described. p
The present invention can also be applied to a semiconductor laser device having a structure in which the type and n-type are interchanged.

Note that the present invention can be applied to devices using other semiconductors in addition to the GaAs-A4GaAe system.

〔Effect of the invention〕

As explained above, in the internal stripe type semiconductor laser device according to the present invention, the current blocking ability is increased because the current blocking layer is doped with an impurity having a deep impurity level to shorten the lifetime of minority carriers. , the current confinement effect is ensured, and stable oscillation can be obtained with a low threshold current.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the structure of a conventional internal stripe type semiconductor laser device, FIG. 2 is a perspective view showing the structure of an embodiment of the present invention, and FIG. 3 is taken along the X-Y line in FIG. FIG. In the figure, (1) is a semiconductor substrate of g51 conductivity type, (2)
) is the current blocking layer of the second conductivity type, (3) is the cladding layer of the first conductivity type, (4) is the active layer of the first conductivity type, and (5) is the second conductivity type.
Conductive type cladding I? i, (91 is the opening. In addition, the same prefecture name in the figure indicates the same or a contrasting part0 Agent Masuo OiwaContinued from page 10 Inventor Toshio Togawa Mizuhara 4-chome, Itami City

Claims (1)

[Scope of Claims] ill A semiconductor substrate having a first conductivity type, a first conductivity type formed on the semiconductor substrate and opposite to the first conductivity type, and a top of the semiconductor substrate and the current blocking layer exposed in the opening. In a device comprising a multilayer semiconductor layer with a double heterojunction structure stacked over the top of the current blocking layer, the current blocking layer is doped with an impurity having a deep impurity level in the semiconductor crystal constituting the current blocking layer. A semiconductor laser device characterized by shortening the diffusion length of minority carriers. (2) A semiconductor laser device according to claim 1, characterized in that the diffusion length of minority carriers in the current blocking layer is made shorter than the thickness of the current blocking layer by doping with an impurity having a deep impurity level. @0 (3) Chromium is an impurity with a deep impurity level. 3. The semiconductor laser device according to claim 1, wherein the semiconductor laser device is doped with one or more of cobalt, iron, and nickel. (4) The semiconductor laser device according to claim 1, 2, or 3, wherein the doping amount of the impurity having a deep impurity level is 1X10'' to 1 x 1017/cm3.