JPS6350876B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a highly reliable visible light semiconductor laser that has good lattice matching with a substrate and is capable of oscillating in a wavelength range up to green. Conventionally, -V group compound semiconductor lasers have been explored as highly practical materials for visible light semiconductor lasers. From a practical point of view, when manufacturing a double hetero-type semiconductor laser, it is necessary to form a double-hetero epitaxial layer on a substrate having good crystallinity and satisfying lattice matching conditions. The shortest wavelength laser material that satisfies these conditions is a double hetero laser with Al _0.5 In _0.5 P on a GaAs substrate as the clad layer and (Al _y Ga _1-y ) _x In _1-x P as the active layer. , Al _0.5 In _0.5 P has a band gap energy Eg of 2.35 ev, and if the Eg difference with the active layer is required to be 0.2 ev, a short wavelength laser of up to ~5800 Å is expected. However, in order to make the wavelength even shorter than this, it is not possible to find a material within the range of the -V group. There are many direct transition type crystals in - group compound semiconductors, and the band eddyluminescence corresponds to blue to red in color. However, the problem with - group compound semiconductors is that most - group crystals do not have good low-resistance P-type crystals. This is the main reason why it has been impossible to fabricate a current injection type semiconductor laser using the - group until now. An object of the present invention is to solve these problems in device manufacturing and to provide a semiconductor laser having high efficiency and high reliability.

The semiconductor laser of the present invention has a band gap energy smaller than the band gap energy at the Γ point of (Al _x Ga _1-x ) _0.5 In _0.5 P, and
An active layer made of a GaAs lattice-matched compound semiconductor is combined with a cladding layer made of n-type ZnSe or ZnSe _1-Y S _Y and a carrier confinement layer made of P-type ZnSe or ZnSe _1-Y S _Y with a thickness of 100 Å or more. It has a laminated structure sandwiched between
The structure includes an optical confinement layer made of type (Al _x Ga _1-x ) _0.5 In _0.5 P. Furthermore, in order to reduce the series resistance, a carrier confinement layer made of n-type ZnSe or ZnSe _1-Y S _Y with a thickness of 100 Å or more is provided in place of the n-type cladding layer, and this layer is further made of n-type ( _Al An optical confinement layer made of Ga _1-X ) _0.5 In _0.5 P is provided.

It is known that GaAs and ZnSe both have a zinc blende crystal structure and have extremely good lattice matching conditions, with lattice constants of 5.653 Å and 5.667 Å, respectively. or
ZnSe is a direct transition type with an energy gap of 2.67eV
It is an important material for shortening the wavelength of visible light semiconductor lasers. However, ZnSe is usually n
However, only P-type crystals are obtained, and the disadvantage of P-type crystals is that they have a high specific resistance. For example, if a 10Ωcm P-type crystal is used as the cladding layer and the film thickness is 2μm, the series resistance of the cladding layer portion of a laser with a stripe width of 10μm and a cavity length of 200μm is 100Ω.
Therefore, good laser characteristics cannot be expected. In a semiconductor laser using ZnSe as a cladding layer, ZnSe plays two roles: carrier confinement in the active layer and light confinement. Since ZnSe has a high specific resistance, it would be desirable to use a thin film, but there are limitations when considering the leakage of light waves corresponding to the oscillation wavelength to the outside of the active layer. Considering this situation, by providing an ultra-thin ZnSe film with a thickness of approximately 100 Å or more adjacent to the active layer as a carrier confinement layer, it is possible to confine carriers in the active layer. It is possible to keep the resistance low. For example, 10
10μm stripe width 200μm with resistivity of Ω・cm
The resistance in the film thickness direction of P-type ZnSe with a cavity length is 1Ω·cm. By making the ZnSe layer ultra-thin, the light confinement effect is weakened, resulting in a large band gap, low absorption at oscillation wavelengths that can be lattice matched to the GaAs substrate, and _low resistivity ( _Al ) _0.5 In _0.5 This defect is covered by using a P-based mixed crystal as a P-type optical confinement layer. At this time, in order to minimize optical absorption with respect to the oscillation wavelength, it is necessary to set the bandgap energy at the Γ point of (Al _x Ga _1-x ) _0.5 In _0.5 P to be at least larger than the oscillation wavelength. A semiconductor laser including the layered structure configured as described above has good characteristics such as low series resistance and therefore low heat generation.
An n-type carrier confinement layer is provided instead of the n-type cladding layer, and an n-type (Al _x Ga _1-x )
The structure with the _0.5 In _0.5 P optical confinement layer means that the same series resistance reduction strategy is also applied to the n-side cladding layer. The structure in which S is mixed into ZnSe (the structure using ZnSe _1-Y S _Y ) is a measure to adjust the slight lattice mismatch (approximately 0.3%) between GaAs and ZnSe.

Next, embodiments of the present invention will be briefly described using the drawings. FIG. 1 shows a planar semiconductor laser, which is an embodiment of the present invention. Ga-doped n-type ZnSe 3 is grown to a thickness of 2 μm on an n-type GaAs substrate 2, and then n-type or P-type or undoped (Al _0.7
Ga _0.3 ) _0.5 In _0.5 P (active layer) 4 is grown to a thickness of approximately 0.1 μm, and then ZnSe 5 doped with nitrogen, phosphorus, arsenic, lithium, etc. to a thickness of 500 Å is grown. On top of that, doped with Zn or Ga etc. to make it P type (Al _0.75 Ga _0.25 ) _0.5 In _0.5
P6 is grown to a thickness of approximately 2μ, and finally n-type GaAs is grown to a thickness of approximately 1μ. Thereafter, a P-type impurity is diffused in the form of stripes 9 using Zn or Cα, and ohmic electrodes 1 and 8 are provided to produce a semiconductor laser. This laser has a wavelength of 5800Å at room temperature.
can oscillate.

FIG. 2 shows a second embodiment of the present invention. Second
In the figure, the first point is that a Ga-doped n-type ZnSe layer 11 of about 200 Å is provided under the active layer 4, and a Se-doped n-type (Al _0.75 Ga _0.25 ) _0.5 In _0.5 P10 is provided below it. This is different from the example. According to the second embodiment, since the series resistance of the semiconductor laser can be further reduced, a semiconductor laser with even better temperature characteristics can be obtained. In both the first and second embodiments, by using ZnS _0.06 Se _0.94 instead of ZnSe, the lattice matching with the GaAs substrate becomes even better, and the reliability as a semiconductor laser is further improved.

In the above example, the active layer was (Al _W Ga _1-W ) _0.5
In _0.5 P was used, but other materials such as ZnSe and GaAs
The effects of the present invention can also be obtained with mixed crystals such as InGaAsP or InGaAsP. In particular, when a mixed crystal of ZnSe and GaAs is used, the band gap energy can be varied in the range from GaAs to ZnSe, which has the advantage of covering a wide wavelength range.

[Brief explanation of the drawing]

FIGS. 1 and 2 are perspective views showing an embodiment of the present invention. In FIG. 1, 1 is an n-type ohmic electrode, 2 is an n-type GaAs substrate, 3 is an n-type ZnSe layer,
4 is an active layer, 5 is a P-type ultra-thin ZnSe layer, 6 is a P-type (Al _x Ga _1-X ) _0.5 In _0.5 P layer, 7 is an n-type GaAs layer, 8 is a P-type ohmic electrode, 9 is a stripe Each shows a P-type diffusion layer. In Figure 2, 10 is n-type (Al _x Ga _1-X ) _0.5 In _0.5 P, and 11 is n-type ultra-thin film.
The ZnSe layer is shown and the other numbers are the same as in FIG.

Claims (1)

[Claims] 1 Band gap energy is (Al _x Ga _1-X ) _0.5
The active layer is made of a compound semiconductor that is smaller than the band cap energy at the Γ point of In _0.5 P and has a lattice match with GaAs, and is made of n-type ZnSe or
It has a structure sandwiched between a clad layer made of ZnSe _1-Y S _Y and a carrier confinement layer made of P-type ZnSe or ZnSe _1-Y S _Y with a thickness of 100 Å or more, and further in contact with the carrier confinement layer. P type (Al _x Ga _1-X ) _0.5 In _0.5 P
A semiconductor laser comprising an optical confinement layer consisting of: 2 Band gap energy is (Al _X Ga _1-X ) _0.5
The active layer is made of a compound semiconductor that has a bandgap energy smaller than the Γ point of In _0.5 P and is lattice matched to GaAs, with a thickness of 100 Å or more.
It has a laminated structure sandwiched between a carrier confinement layer made of type ZnSe or ZnSe _1-Y S _Y and a carrier confinement layer made of p-type ZnSe or ZnSe _1-Y S _Y with a thickness of 100 Å or more, and further includes the n-type carrier confinement layer. an optical confinement layer made of n-type (Al _x Ga _{1 - x} ) _{0.5 In 0.5} P in contact with the confinement layer _; A semiconductor laser comprising an optical confinement layer consisting of: