JPH067629B2 - Semiconductor laser - Google Patents

Description

TECHNICAL FIELD The present invention relates to a material for an end face protective film for preventing deterioration of a semiconductor laser and obtaining stable operation for a long time.

[Outline] The present invention provides a single crystal ZnSSe as an end face protective film of a semiconductor laser made of an AlGaAs-based, In (GaAl) P-based or InGaAsP-based material.
By adopting a film, a stable operation of the semiconductor laser is obtained.

[Prior Art] In recent years, a semiconductor laser has been remarkably extended in life as compared with the initial stage of research and development. Semiconductor lasers have fast deterioration and slow deterioration.It is said that the fast deterioration is mainly caused by lattice defects in the crystal, but the slow deterioration is considered to be caused by optical damage on the cleavage plane. There is. This photodamage is caused by the photochemical reaction of the cleaved surface with oxygen gas in the atmosphere by the laser light emitted from the cleaved surface. Therefore, it has been proposed to cover the cleaved surface with an oxide film in order to prevent oxidation at the cleaved surface. Japanese Patent Sho 58
No. -50037 has 200 AlGaAs semiconductor laser crystal plates.
The invention discloses that an Al ₂ O ₃ film was vapor-deposited as a protective film on the cleavage surface by heating at a temperature of ℃ or more. On the other hand, in JP-A-59-39082, a resonator end face of a semiconductor laser made of AlGaAs-based material is coated with each material of Si ₃ N ₄ , SiO ₂ , Al ₂ O ₃ and ZnSe. It is shown that it was the most excellent end face protective material. Here, the ZnSe film is a single crystal formed by the MBE method, but other films are plasma CVD,
It is an amorphous film formed by sputtering and vapor deposition.

[Problems to be Solved by the Invention] When an amorphous film such as SiO ₂ or Al ₂ O ₃ is used in a conventional protective film, pinholes are often generated, which results in large adsorption and permeation of water, oxygen, etc. There is a defect that the adhesion of the protective film is not good and the end face protection does not function sufficiently. Moreover, even if the lattice constant of the protective film is made to be close to that of the semiconductor laser by using a ZnSe single crystal film, the lattice constant is constant and further approximated, and the lattice constant is controlled for the semiconductor laser of other composition. I couldn't do that. The present invention solves such a conventional problem.

[Means for Solving Problems] In the present invention, the above problems are solved by growing a ZnSSe single crystal as an end face protective film on the resonance surface of a semiconductor laser made of AlGaAs, InGaAlP, InGaAsP. This ZnSSe single crystal is formed by vapor phase epitaxial method such as MOCVD method (metal organic chemical vapor deposition method), MBE method (molecular beam epitaxial method) and liquid phase epitaxial method.

[Operation] The lattice constant of GaAs is 5.65325A and the lattice constant of AlAs is 5.6605A.
And the lattice constant of Al _X Ga _1-X As is 5.65325 + (5.6605-5.653
25) It becomes XA. Here, the lattice constant of Al _0.4 Ga _0.6 As in the case of X = 0.4 is 5.65615A, which is a good approximation to the lattice constant of GaAs, and the lattice constant coincidence rate Δa / a (a: lattice constant of GaAs,
Δa: difference in lattice constant between GaAs and AlGaAs) is 10 ^{−4, which} is negligibly small. When a ZnSe edge crystal is grown as a protective film on this semiconductor laser made of GaAs and Al _0.4 Ga _0.6 As, the lattice constant of ZnSe is 5.6686 A, so the matching rate Δa / a of the lattice constant is 10 ^−3. And grows. However, when the ZnS _X Se _1-X single crystal disclosed in the present invention is adopted as the protective film, since the lattice constant of ZnS _X Se _1-X is 5.6686-0.2586X, the single film of the protective film is X = 0.059. Crystal lattice constant and GaAs
Of the ZnSe and the coincidence rate △ a / a is 10 ^-4 .
It is significantly improved compared to 10 ^-4 . Thus, GaA
Since the lattice constants of s, AlGaAs and InGaAlP and the lattice constant of the ZnSSe film are very close to each other compared to other materials, ZnSSe single crystal is used as an end face protective film on the intermetallic compound crystal that becomes a semiconductor laser. When grown, the crystallinity of the interface between the two is kept good. As a result, the occurrence of pinholes and the like, and the strain due to the change in lattice constant are eliminated.

Embodiments Embodiment (i) For example, as shown in the accompanying drawings, n is used as a first cladding layer on a semi-insulating N ⁺ GaAs substrate crystal 2.
Type Ga _0.6 Al _0.4 As layer 3, undoped Ga _0.95 Al as active layer
_0.05 As layer 4, P-type Ga _0.6 Al _0.4 As as the second cladding layer
5, and a P-type GaAs layer 6 as a cap layer was sequentially formed by the MOCVD method. An oxide film 7 was provided thereon, an opening was formed in a stripe shape, and a metal layer 8 serving as an upper electrode and a metal layer 1 serving as a lower electrode were provided on one surface. After that, the wafer is cleaved to form strip-shaped substrates, and single-crystal ZnS _0.06 Se _0.94 is used as MOC on both sides of the substrate as end face protective films 9.
It was grown by the VD method. DMZ as the source at this time
(Dimethylzinc), DEZ (diethylzinc), H ₂ S, H ₂ Se, etc. were used to perform crystal growth at a low temperature of 250 ° C. to 350 ° C. Next, a strip substrate on which single-crystal ZnSSe was grown as the end face protection film 9 on both sides was cut into chips, which were mounted and packaged to obtain a semiconductor laser.

Iny instead of AlGaAs in the embodiment (ii) Example _{(i) (Ga 1-X} A X) 1-Y P (Y = 0.5,0 <X <1) using crystalline.

Example (iii) In _X Ga _1-X As _Y P _1-Y was used instead of AlGaAs in Example (i).
((1-y) = 2.04X) crystal was used.

[Effect of the Invention] GaAs, InGaAlP, since adopting a ZnS _X Se _1-X single crystal as an end face protective film of a semiconductor laser made of InGaAsP, the rate of matching lattice constants △ a / a is a conventional 10 ^-3 to 10 ^- It has dramatically improved to ⁴ . Since the crystallinity of the interface between the semiconductor laser and the end face protective film is improved, and the adherence of the end face protective film is improved,
Adsorption and permeation of water and oxygen, damage to the cleavage surface, corrosion, and oxidation were prevented, enabling a longer life of the semiconductor laser. Zn
When the SSe single crystal film is formed by the MOCVD method using DMZ or DEZ, the forming temperature can be lowered to 250 ° C to 350 ° C. This is very useful in that the end face protective film is formed at the final stage of the semiconductor laser manufacturing process, and it is not necessary to apply high heat to the almost completed semiconductor laser. Furthermore, according to this method, a large number of charges can be performed at one time, the throughput is large, and the mass productivity is improved.

[Brief description of drawings]

The drawing is a sectional view of a semiconductor laser. 1 ... Electrode 2 ... Semi-insulating N ⁺ GaAs substrate crystal 3 ... n-Ga _0.6 Al0.4As 4 ... Undoped Ga _0.95 Al0.05As 5 ... P-Ga _0.6 Al0.4As 6 ... P-GaAs 7 ... Oxide film 8 ... Electrode 9 ... End face protection film

Claims (2)

[Claims] 1. A semiconductor laser comprising a ZnSSe single crystal film as an end face protective film of a semiconductor laser made of an AlGaAs type, In (GaAl) P type or InGaAsP type material. 2. The semiconductor laser according to claim 1, wherein the ZnSSe single crystal is formed by the MOCVD method.