JPH0770779B2 - Semiconductor laser manufacturing method - Google Patents

Description

The present invention relates to a semiconductor laser capable of stable oscillation in a transverse mode, and in particular, has a small leakage current in regions other than the light emitting region of the semiconductor laser and has crystal defects introduced into the light emitting region. The present invention relates to a semiconductor laser whose reliability is improved by making it harder to operate.

[Background of the Invention]

The conventional self-aligned structure semiconductor laser has the following structure shown in the literature such as JJ Coleman. That is,
As shown in FIG. 2, n- (GaAl) As is formed on the n-type GaAs substrate 1.
Cladding layer 2, undoped (GaAl) As active layer 3, p-
After forming the (GaAl) As cladding layer 4 and the n-GaAs light absorbing layer 5 and removing a part of the light absorbing layer in a stripe shape by etching and embedding p- (GaAl) As6, p for forming an electrode is formed. -A crystal growth of GaAs layer 7 (Coleman et al.,
Applied Physics Letters Vol. 37, p. 262 1
980 (JJ Coleman et al., Appl.Phys.Lett.Vol 37
(3), p.262, 1980), the current confinement and the formation of the waveguide are simultaneously performed by the light absorption layer.
When forming by using crystal growth in a thermal non-equilibrium state such as MOCVD or MBE, there are crystal defects due to crystal growth on steps and the growth interface of double growth in electrically and optically active regions. Therefore, the reliability of the element was lowered.

[Object of the Invention]

The present invention prevents a reduction in device life due to crystal defects caused by crystal growth on a substrate with steps and defects at the growth interface of double growth, which are problems in the conventional self-aligned semiconductor laser. To provide a laser.

[Outline of Invention]

The present invention prevents a decrease in device life due to crystal defects due to crystal growth on a substrate having a step and defects at a double-growth growth interface, which are problems in a conventional self-aligned semiconductor laser. Instead of filling (GaAl) As in the stripe with high current and light density, stripe-shaped SiO ₂ or Si is formed on the p-type cladding layer outside the stripe.
Etching the p-type cladding layer using an insulator mask such as ₃ N ₄ so that crystal growth does not occur on the insulator but only on the outside of the stripe. The present invention relates to a semiconductor laser using a III-V group compound semiconductor material having a zinc blende type crystal structure for forming a.

Example of Invention

 Embodiments of the present invention will be described below with reference to the drawings.

Example 1 FIG. 1 shows a sectional structure of a semiconductor laser according to this example. The manufacturing process of this structure is as follows.

n-Ga _0.55 Al on n-GaAs substrate 1 by atmospheric pressure MOCVD method
_{After the 0.45} As cladding layer 2, the undoped Ga _0.88 Al _0.14 As active layer 3, the p-Ga _0.55 Al _0.45 As cladding layer 4 and the p-GaAs cap layer 8 were successively grown, SiO ₂ was formed by using a normal photolithographic technique. A mask 13 is provided, and a phosphoric acid-based etching solution is used to form a p-type cladding layer 0.1 to
Etching was performed leaving 0.3 μm. FIG. 3 shows the cross-sectional structure of the device at this stage. The structure thus manufactured was again embedded with n-GaAs 9 by the MOCVD method. Here, when the stripe orientation is [10] direction, as shown in FIG. 4, growth occurs from the side surface of the ridge, and sharp protrusions are formed on both sides of the stripe, so that the stripe orientation is [110] direction. It is necessary to make the angle 14 of the side surface of the ridge with respect to the substrate surface 100 degrees or less by a method such as using a dry etch, and preferably to make the ridge shape into an inverted trapezoidal shape as shown in the figure. . In this case, MOCVD without crystal growth on the SiO ₂ film
Due to the characteristics of the method, the SiO ₂ film remained exposed and could be removed with a hydrofluoric acid-based etching solution after the buried growth. In this structure, Cr / Au10 is used as the p electrode and AuG is used as the n electrode.
eNi / Cr / Au11 was vapor-deposited and cut into a 300 μm square to form a laser chip.

Example 2 As a second example, a p-type cladding layer was formed of p-Ga _0.55 Al.
An element having a structure as shown in FIG. 5 was _manufactured by using a double-layered structure of p-Ga _0.6 Al _0.4 As layer 4 and p-Ga _0.35 Al _0.55 As layer 12 instead of the _0.45 As layer 4-layer. Here, the thickness of the p-Ga _0.7 Al _0.3 As layer 4 was set to 0.1 to _0.3 μm. In this structure, the p-Ga _0.5 Al _0.5 As layer is formed by using an iodine-based etching solution.
12 can be selectively removed with respect to the p-Ga _0.6 Al _0.4 As layer 4. Hereinafter, a semiconductor laser chip was manufactured by the same process as in Example 1.

[Brief description of drawings]

FIG. 1 is a sectional structural view of a semiconductor laser of Example 1, FIG. 2 is a sectional structural view of a conventional self-aligned semiconductor laser, and FIG. 3 is a sectional structural view of a semiconductor laser of Example 1 before buried growth. ,
FIG. 4 is a cross-sectional structure diagram when buried growth is performed in stripes in the <110> direction, and FIG. 5 is a cross-sectional structure diagram of the semiconductor laser of the second embodiment. 1 ... n-GaAs substrate, 2 ... n-Ga _0.55 Al _0.45 As cladding layer, 3 ... undoped Ga _0.86 Al _0.14 As active layer, 4 ...
p-G _0.55 Al _0.45 As cladding layer, 5 ... p-GaAs light absorption layer, 6 ... p- (GaAl) As layer, 7 ... p-GaAs, 8 ...
p-GaAs cap layer, 9 ... n-GaAs layer, 10 ... Cr / A
u, 11 …… AuGeNi / Cr / Au, 12 …… p−Ga _0.5 Al _0.5 As layer, 1
3 …… SiO ₂ mask, 14 …… Angle between the substrate and the side of the ridge

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Kajimura 1-280 Higashi Koigakubo, Kokubunji City, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (56) References JP-A-53-29687 (JP, A) JP-A-57 -152180 (JP, A) JP 59-56783 (JP, A) Journal of Crystal Growth 73 (1985) P. 73 to P. 76 J. J. A. P. Vol. 25, No. 6, June, 1986, PP. L498-L500

Claims (2)

[Claims] 1. A substrate, an active layer formed on the upper portion of the substrate, a clad layer having a ridge-shaped stripe formed on the active layer, and a layer formed on the clad layer to fill the outside of the stripe. A semiconductor laser manufacturing method for manufacturing a semiconductor laser using a III-V group compound semiconductor material having a zinc blende type crystal structure by a crystal growth method in a thermal non-equilibrium state, wherein: A layer for embedding the outside of the stripe is grown on the cladding layer by using the crystal growth method, with the orientation being the [110] direction and the angle of the ridge-shaped side surface with respect to the substrate surface being 100 degrees or less. Of manufacturing a semiconductor laser. 2. The crystal growth method in the thermal non-equilibrium state is MOCVD.
The method of manufacturing a semiconductor laser according to claim 1, wherein the method is a method.