JPS61272988A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To prevent a crystal defect on crystal growth onto a substrate with a stepped section by previously forming a recess to the substrate and matching a waveguide, which is shaped to the upper section of a semiconductor laser and does not absorb laser beams, with an active layer on a laser end-surface. CONSTITUTION:An N-Ga0.55Al0.45As clad layer 9, an undoped Ga0.86Al0.14As active layer 10, a P-Ga0.55Al0.45As clad layer 11, a P-GA0.55Al0.45As layer 12, a P-Ga0.55Al0.45As layer 13 and a P-GaAs cap layer 14 are crystal-grown on an N-GaAs substrate 8, to which a groove is shaped, in succession. The layer 12 and the active layer 10 are superposed in the groove section in the substrate at that time. The outside of a stripe is etched while leaving the P-type clad layer in 0.1-0.4mum, and buried from the layer 13. In the structure, Cr/Au 14 as a P electrode and AuGeNi/Cr/Au 15 as an N electrode are evaporated, and the whole is cloven at the intervals of 300mum at the positions of broken lines, thus manufacturing laser chips.

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to the structure and manufacturing method of a semiconductor laser that can operate at high output in a stable transverse mode, and in particular to a structure and manufacturing method for a semiconductor laser that can operate at high output in a stable transverse mode. The present invention relates to the structure and manufacturing method of a semiconductor laser that enables output operation. [Background of the Invention] As shown in FIG. 1, a conventional self-aligned structure semiconductor laser has n-(GaAffi)As on an n-type GaAt5 substrate 1.
Cladding layer 2, undoped (GaAQ)As active layer 3.
P-(GaAjl)As cladding layer 4, n-Ga
A s light absorption layer 5 is formed, and a part of the light absorption layer is removed in a stripe shape by etching to form P-(GaAjl)A.
After implantation with s6, p -G a A for electrode formation
Coleman et al., “Longitudinal single-mode property of CVD self-aligned GaAQAs-GaAs double heterostructure semiconductor laser,” Applied Physics Letters, Vol. 37. 1980 pp. 262-263 (J, J, Colam
an at al“Single-1ongitudi
nal-mode matalorganicch
chemical-vapor-deposition
self-alignedGaAs-Ga
A s double-haterostructure
alasers"Appl, Phys, Lett, 3
Yu, 1980. p, 282-263), current interpolation and waveguide formation are performed simultaneously using a light absorption layer, but when this structure is formed using crystal growth in a thermal non-equilibrium state such as MOCVD or MBE, , crystal defects due to the length of the crystal edge on the step, and the growth interface of the double growth are electrically
Since it is located in an optically active region, the reliability of the device is reduced. Furthermore, destruction of the end face due to absorption of laser light at the laser end face has been an obstacle to high output operation.

[Purpose of the invention]

The present invention prevents a decrease in device life due to crystal defects caused by crystal growth on a substrate with a zero-step difference and defects at the growth interface during double growth, which were problems in self-aligned semiconductor lasers with a conventional structure. An object of the present invention is to provide a semiconductor laser capable of high output operation by making the laser end face transparent to laser light. [Summary of the Invention] Crystal defects associated with crystal growth on a stepped substrate, which were problems in conventional self-aligned semiconductor lasers,
In order to prevent a decrease in device life due to defects at the growth interface caused by double formation, in the present invention, instead of filling the inside of the stripe where the current and light density is high with (GaAΩ)As,
By partially removing the p-type rad layer outside the stripe,
In a structure embedded with a As or (G a A 5) As having a smaller refractive index than the cladding layer,
A waveguide provided above the semiconductor laser that does not absorb laser light is aligned with the active layer at the end face of the laser by previously providing a recess in the substrate at the end face of the laser. [Embodiments of the Invention] Hereinafter, the present invention An example will be explained according to the drawings. Example 1 An n-Ga 01. $A
Q,,,5 A s cladding layer 9, undoped G 6
．． ,,A fio,1. As active layer 10, p-Ga
, , B A n , , 4sA B Clarad layer 11
, p-G a@, siA Q6,3@A s layer 12, p
-G a 6 , ss A na , <s A 8 layer 1
3. A p-GaAs cap layer 14 was successively crystal-grown. At this time, in the groove part of the substrate, the position of each layer is lowered by the depth of the groove, so p-G a, ..., A
jl,..., As layer 12 and undoped Ga 11.
11! A II a, t4A 8 active layer 10 is the third
As shown in Figure (b), an SiO mask was formed using the normal photolithography technique, and the outside of the stripe was etched into a p-type layer by 0.1% using a phosphoric acid-based etching solution. Etch leaving ~0.4 μm, n-G
a, , , , A (embedded by 1, 0,, A s 13, at this time Sin, MO which is difficult to form precipitates on the film)
Due to the characteristics of the CVD method, the Sin film remained exposed and could be removed using a hydrofluoric acid-based etching solution after buried growth. In this structure, Cr/Au14 is used as a p-electrode.
A u G e N i /Cr /
Deposit A u 15 to 300μ at the position of the broken line in Figure 1.
A semiconductor laser according to the present invention, which is made into a laser chip by dividing it at intervals of m, has a threshold current of 30 mA and an oscillation wavelength of 7.
Continuous oscillation at room temperature at 80 nm, 70 nm at constant light output of 5 mW.
As a result of the °C accelerated life test, no significant deterioration was observed up to 300 hours. Example 2 As a second example, a p-shaped rad layer is formed by p −Ga
a , ss A na , as A p-G a a , t A ne , s A between the s layer 11 and the active layer
An element having a structure as shown in FIG. 3, in which the s-layer 18 was provided, was fabricated as a prototype. Here, in this structure in which the thickness of the p-Gao, 7A Jla, aAs layer 18 is set to 0.1 to 0.31 m, by using an iodine-based etching solution, the p-Q B
,,,A fill, 4gA 8 layer 18 p Ga
@ , 7 A n @ 0 g Since the A s layer 11 can be selectively removed, the difference in refractive index inside and outside the stripe can be easily controlled.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the structure of the substrate crystal, FIG. 2 is a diagram showing the cross-sectional structure of a conventional self-aligned semiconductor laser, FIG. 3 is a diagram showing the cross-sectional structure of the semiconductor laser of Example 1, and FIG. The diagram is
3 is a cross-sectional structural diagram of a semiconductor laser of Example 2. FIG. 1-n-type GaAs substrate, 2-n-(GaAl)
As cladding layer, 3... undoped (GaAn) As
Active layer, 4-p-(GaAn) As
Cladding layer, 5-n-Ga As light absorption layer, 6
-P-(GaAn)As. 7-p-GaAs layer, 8-n-GaA15 substrate, 9-n-GaA6. ssA A6. ssA 8
Cladding layer, 10-... undoped Ga a, , @A
11B, 14A s active layer, 11...p Ga,
,,,A a, ,,A s cladding layer, 12 ・p-
〇 all, 7A 416.3A s layer, 13-P-G
a1), ss A Q o, 41 A 8 layers,
14- p -Ga As cap layer, l 5-1
l-Ga, 4. Ajl. 6. , As, 16-Cr/A
u, 17- A u G e N i / Cr /
Au, 18-p-Ga, , Al, 3. As layer, 1
900 1 Figure ■ J Figure

Claims (1)

[Claims] 1. At least a first semiconductor layer, and second and third semiconductor layers, which are provided to sandwich the first semiconductor layer and have a wider forbidden band width than the semiconductor layer and different conductivity types. In a structure having a semiconductor layer, the third semiconductor layer is removed except for the striped portion of the third semiconductor layer, leaving 0.1 to 0.4 μm, and a third semiconductor layer having a refractive index smaller than that of the third semiconductor layer is removed. In the semiconductor laser which is replaced by the fourth semiconductor layer, a fifth semiconductor layer is provided on the third semiconductor layer and has a larger refractive index than the third semiconductor layer and a wider forbidden band width than the first semiconductor layer. Then, a sixth semiconductor layer having a refractive index smaller than that of the fifth semiconductor layer is provided, and by providing a depression in advance in the substrate crystal near the end facet of the semiconductor laser, the fifth semiconductor layer is formed near the end facet to form a recess in other parts. A semiconductor laser device characterized by being aligned with a first semiconductor layer. 2. A patent claim characterized in that the depth of the recess provided in the substrate crystal is deeper than the thickness of the third semiconductor layer and shallower than the sum of the thicknesses of the first, third, and fifth semiconductor layers. The semiconductor laser device according to item 1. 3. MOC that grows crystals while preserving the shape of the substrate crystal
A semiconductor laser device formed using crystal growth technology in a thermal non-equilibrium state, such as the VD method or MEB method.