DE3012361A1 - Semiconductor laser - with diffusion front at specified approach to laser active layer - Google Patents

Abstract

The parent patent no. 2822146 described a semiconductor laser with a sequence of layers in the form of a heterostructure diode. Diffusion of a dopant through the structured surface has produced a diffusion front which extends nearly to the laser active zone. The distance of the diffusion front from the laser-active zone is made so short (0-0.5 mu) that a substantial part of the optical laser light penetrates into the diffusion front. This yields an optimum distance which increases the laser stability by maximising the near field with of the laser emission and by reducing the effective refractive index below the surface groove.

Description

ilaible conductor laser

Addition to patent ... ... ... (patent application P 28 22 146.7) The invention relates to a semiconductor laser according to the preamble of claim 1.

Such a flaltleiterlaser is in the main application P 23 22 146.7 and in FIG. 1 outlined. There are five layers on the substrate 1 2 to 6, with a V-shaped groove etched into the top layer 6 so as to suitably shape the diffusion region 7. In general, this is the diffusion range p-conductive, so that with p-conductive layer 4 and n-conductive layer 5 the current path limited to a width B at the interface between layer 4 and layer 5 will.

The object of the invention is to provide an advantageous choice of the distance d indicate the diffusion front from the laser-active zone. The invention is in Claim 1 specified. The subclaims contain further advantageous stick Embodiments of the invention.

In the main application P 28 22 146.7 it is already pointed out that that for a stable laser emission an emission in the transverse fundamental mode of the Laser is necessary, for which a current injection is required in a narrow strip area needed. (For stability see e.g.

R. Lang, "Lateral mode instability and its stabilization in stripe geometry injection lasers ", IEEE J. Quant. E.C. QE-15 (1979), pp. 718 bis 726).

A closer look shows that the near field width for stable lasers the laser emission must be of the same order of magnitude or greater than the width the charge carrier distribution injected into the active zone 3.

One way to achieve this goal is to go further the injected charge carrier distribution through the small width B of the diffusion front to keep very narrow, as described in the main application P 28 22 146.7.

According to the invention, it is proposed here that B not necessarily be too small but the near field width of the laser emission through suitable dimensioning of d, the distance between the diffusion front and the laser-active zone, as large as possible to choose. This is possible if part of the run in the active zone 3 Light reaches into the diffusion area 7. In addition, d is typically smaller than 0.5 / um to choose. Given the above, is the effective refractive index decreased below the trench (p-diffusion in p-material leads to a decrease the refractive index, see e.g. B.

D. D. Sell et. al. t'Concentration dependence of the refractive index for n- and p-type GaAs between 1.2 and 1.8 eV ", 7th Appl. Phys. 45 (1974), 5. 2650 to 2657), so that a negative Waveguide results, with such a negative waveguide leading to a broadening of the near field of the laser emission.

Under these conditions, the width of the injected can also be determined Load carrier distribution or B larger, typically Bm 5 ... lOfum, can be selected, and the laser nevertheless shows a stable emission behavior because the near field of the Laser emission becomes even wider due to the built-in negative waveguide.

Being able to adjust tm B and d independently of one another is advantageous instead of the V-groove in FIG. 1 a trapezoidal groove 8 according to FIG. 2 used that one obtained in the same way as the V-groove in FIG. 1 according to the main application P 28 22 146.7, except that either the width of the masking was chosen to be larger or the etching time shorter is chosen.

Such a solution according to the invention is shown in FIG. 2 shown.

An advantage of the trapezoidal groove 8 is that the Layer 6 thinner than in FIG. 1 can be selected, so that the absolute production-related Fluctuations in the layer thickness of 6 also turn out to be correspondingly smaller and thus a more precise diffusion is possible.

In a running example, B6 is up to 8µ, dz (0.5 / u and the individual layers are grown using liquid phases as follows: (1) Ga As substrate n-doped (Si 1.3, 1018 cm 3), thickness 80 / µm.

(2) Ga 1-x Al As layer n-doped (Te 2. 1017 cm-3), thickness 5 µm x = 0.3 - 0.35 (3) Ga1-y Aly As layer, thickness 0.2 µm, y = 0.02 (4) Ga1-z1, Alz1 As layer p-doped (Ge 5. 1017 cm-3), thickness 2 / um z1 = 0.4 (5) Ga1 Alz As layer n-doped (Te 2 - 3.1017cm-3), 1-z2 Alz2 thickness 1 / um z2 = 0.4 (6) Ga As layer n-doped (Te 2 - 3, 1017 cm 3), thickness 3 / µm.

The laser produced in this way has a kink-free light-current characteristic up to the maximum permissible mirror load and also shows a low level of noise.

Claims (5)

Patent claims Addition to patent ... ... ... (patent application P 28 22 146.7) 1. Semiconductor laser with one in the form of a heterostructure diode Layer sequence in which an essentially homogeneously doped laser-active zone on both sides is enclosed by two differently doped semiconductor layers, and wherein means for constricting the current flowing in the forward direction of the diode are provided on a narrow, strip-shaped area of the laser-active zone, wherein a monocrystalline layer is also provided, which is in the layer sequence above one of the differently doped semiconductor layers or one on top of it Applied additional layer is arranged and the gate surface is a substantially Trench-shaped depression running perpendicular to the exit surface of the laser radiation having, and wherein by diffusion of doping material through the structured Surface through generated semiconducting regions of different doping provided are which through a diffusion front corresponding to the structured surface are separated from each other in such a way that below the trench-shaped depression a until Semiconducting area of im reaching to the laser-active zone essentially the same conductivity type is formed, according to patent application P 28 22 146.7, characterized in that the distance (d) of the diffusion front of the laser-active zone (3) is so small that a substantial part of the optical Laser light penetrates into the diffusion area (7) (FIG. 2). 2. Semiconductor laser according to claim 1, characterized in that the Distance (d) of the diffusion front from the laser-active zone (3) between 0 and 0.5 / μm lies. 3. semiconductor laser according to claim 1 or 2, characterized in that that on the laser-active zone (3) there is a p-conductive layer with a higher band gap (4), then an n-type layer (5) and finally a p- or n-type layer (6) adjoins and that the diffusion region (7) extends into the p-conductive layer higher band gap (4) extends. 4. Semiconductor laser according to one of the preceding claims, characterized characterized in that the width B with which the diffusion front the interface between p-type layer (4) and n-type layer (5) penetrates, between 4 and 10 / um. 5. Semiconductor laser according to claim 1, characterized in that the Trench-shaped depression is designed as a trapezoidal groove (8).