JPH0472787A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To prevent a laser beam from deteriorating in quality keeping it short in wavelength by a method wherein a second conductivity type first clad layer above an active layer is provided with a stripe-like inverted mesa structure which is formed making the clad layer partially large in thickness and made to extend in a [011] direction, and a semiconductor layer is provided to both the sides of the mesa structure to bury the mesa structure. CONSTITUTION:An N-type (Al0.6Ga0.4)0.5In0.5P clad layer 2, a Ga0.5In0.5P active layer 3, a P-type (Al0.6Ga0.4)0.5In0.5P clad layer 4, and a P-type GaInP layer are successively formed on an N-type GaAs substrate 1. A stripe-like Sin. mask 9mum in width is formed in a <011> direction through a photolithography method on the wafer grown as above. The substrate 1 is etched into a mesa shape up to a halfway point of the P-type (Al0.6Ga0.4)0.5In0.5P clad layer 4 using a hydrochloric acid etching solution. In succession, A second growth process us carried out through a vacuum MOVPE keeping the SiO2 mask attached to the surface of the substrate 1 to form an N-type GaAs layer 6. Then, after the SiO2 mask is removed, a third growth process is executed through a vacuum MOVPE to form a P-type GaAs layer 7. Lastly, a P and an N electrode are provided, and the wafer is cleaved so as to be 300mum in cavity length and separated into chips.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an AlGaInP semiconductor laser that oscillates in a single transverse mode.

[Conventional technology]

Recently, a single transverse mode oscillating A
As an lGaInP-based semiconductor laser, the structure shown in Figure 3 has been reported (Electronics Letters (ELECTI), 0NIC8LETTER86th
July 1989 Mo1.14pp905-
907)).

This structure was formed by (511)-faced n-type Ga in the first growth.
On the As substrate l, n-type (Alo, s Ga6,4) o
, 5In6,5P cladding layer 2. GaInP active layer 3.
p-type (Alo, s Ga6,4 ) o, s I r
lo, 5P cladding layer 4. p-type layer aInP layer5. are formed sequentially. Next, 5i01 was created using photorin graphie.
is used as a mask to form mesa stripes. and 5
A second growth is performed with the i02 mask on, and the etched areas are filled with an n-type GaAs layer 6. Next, the 8i01 mask is removed, and a p-type GaAs layer 7 is grown in a third growth so that an electrode can be formed on the entire p-side surface.

With this structure, current is blocked by the n-type GaAs layer 6 and is injected only into the mesa stripe portion.

Furthermore, during etching to form mesa stripes, the thickness of the p-type cladding layer 4 other than the mesa stripe portion is etched to a thickness insufficient for confining light, so nmGa
In a certain portion of the As layer 6, light is absorbed by the n-type GaAs layer 6, and the light is guided only to the mesa stripe portion. In this way, in this structure, the current confinement mechanism and the optical waveguide mechanism are built at the same time.

More MOVPEK! D In the AlGaInP crystal grown on the (100) GaAs substrate, a natural lattice is formed on the group II sublattice depending on the growth conditions, and compared to a complete mixed crystal, the band gear and energy are smaller and the oscillation wavelength is longer. The phenomenon is known. In general, the conditions for growing crystals for lasers are such that a natural lattice is formed on the group III sublattice, and the band gear and energy are smaller than in a complete mixed crystal, resulting in a longer oscillation wavelength due to factors such as doping characteristics. It ends up. Against this 100)
In an AlGaInP crystal grown on a GaAs substrate tilted in the [011) direction from the plane, as the tilt increases, the formation of a natural superlattice is inhibited, and at ±10' or more, the band gap energy of a complete mixed crystal decreases. The value is almost equal to . Therefore, it becomes easier to obtain a laser with a short wavelength, which is advantageous for applications such as optical information processing.

[Problem to be solved by the invention]

In the structure shown in Figure 3 above, from the (100) plane, [011]
Since a crystal tilted in the direction is used, it is necessary to cut the stripe in the [O1l] direction in order to form a parallel misalignment due to the cleavage plane. At this time, the angles of the left and right side surfaces of the mesa stripe with respect to the substrate differ as shown in FIG. This causes asymmetry in the refractive index distribution on the left and right sides of the mesa stripe, distorting the light distribution and degrading the quality of the laser beam.

An object of the present invention is to solve the above-mentioned problems and provide an AlGaInP-based semiconductor laser with a transverse mode control structure that prevents deterioration of laser beam quality while keeping the oscillation wavelength short.

[Means to solve the problem]

In the semiconductor laser of the present invention, the substrate surface is closer to the (100) plane [
011) The first tilted in the direction of ±10° or more and ±30″ or less
GaInP or A on the conductivity type GaAs substrate
A double heterostructure is formed, consisting of an active layer made of lGaInP or a quantum well layer thereof, and a cladding layer made of AlGaInP with a refractive index smaller than that of the active layer, sandwiching this active layer. The first cladding layer of two conductivity types has a striped inverted mesa structure in the [O1l] direction, which is formed by partially increasing the layer thickness, and at least semiconductor layers are provided on both sides of the mesa structure. It is characterized by having a structure in which a mesa structure is embedded.

[Effect]

In the semiconductor laser of the present invention, [O1l
] A laser structure is formed on a GaAs substrate with a plane orientation tilted in the direction. (lOO) When an AlGaInP crystal is grown on a GaAs substrate with a plane orientation tilted in the [011] direction from the WJ, the tilt range is small (0° to 66).
In this case, the formation of a natural superlattice is promoted, and the band gap energy becomes smaller. However, when the tilt exceeds ±10', the formation of a natural superlattice is suddenly inhibited, and the oscillation wavelength is tilted from the (100) plane to the [011) direction, making it short as in the conventional example using nine crystals. I can do it. and (l
When forming a laser structure on a GaAs substrate tilted in the [011) direction from the 00) plane, the trap must be striped in the [011] direction in order to form a parallel mirror by the cleavage plane. At this time, the shape of the mesa stripe becomes an inverted mesa. In the case of an inverted mesa shape, even if the angles of the left and right sides of the mesa stripe with respect to the substrate are different, the refractive index distribution changes rapidly on both sides, so there is no asymmetry in the refraction/heavy distribution on the left and right sides of the mesa stripe, and the light distribution is Since there is no distortion, the quality of the laser beam does not deteriorate.

〔Example〕

Embodiments of the present invention will be described using the drawings.

FIG. 1 is a sectional view of a first embodiment of a semiconductor laser according to the present invention.

First, with the first decompression MOVPE growth, (511)
B-plane n-type GaAs substrate 1 (8i doped; n=2X
10” cm-3), n-type (Alo, soaO
,,)o,5In(1,5F cladding layer 2(n=5X1
0 cm: thickness 1 μm), oa (L5 Ing,
5 P active layer 3 (undoped; thickness o, 1 μm), p-type (Alo, s Ga a, a ) o, s I no
, sP cladding layer 4 (p=5 X 1 o"cm-3
; thickness 1.0 μm), p-type layer aInP layer 5 (p=l
xto Cm: thickness 03 μm) were sequentially formed.

The growth conditions were a temperature of 700°C, a pressure cuff of 0 Torr,
V/1I=200, and the total flow rate of carrier gas (H2) was 1517 m1n. As a raw material, trimethylindium A (TMI: (CHs)s I n )
, triethylgalliu A (TEG: (C2H,)3Ga
), trimethylaluminum (TMA: (CHs
)s kl ), ak syn (AsH3), phosphine (PH3), n-type dopant: hydrogen selenide (H,8e
), p-type cyclopentadienylmagnesium (CpzMg) was used.A striped 5i02 mask with a width of 9 μm was formed in the <011> direction on the thus grown Weno 1 by photolithography.Next Then, p-type (AA!o, sGa
α4) 0.5 I no, s The middle of the P cladding layer 4 (here, 0.8 μm) was cut into a mesa shape. Next, decompression MOVP with the 8102 mask on.
A second growth was performed using E to form an n-type GaAs layer 6.

After removing the 8i0z mask, vacuum MOVPE
A third growth was performed to form a p-type GaAs layer 7. Finally, both p and n electrodes (not shown) were formed and separated into individual chips with a cavity length of 300 μm.

The oscillation wavelength of the semiconductor laser manufactured in this way is (511)
It oscillated at about 660 nm, the same as a conventional semiconductor laser formed on an A-plane GaAs substrate. The oscillation wavelength of a semiconductor laser grown on a (100) GaAs substrate under the same conditions as in this example is 688 nm, which is shortened by 28 nm in this example. Furthermore, the near-field image in the direction parallel to the junction surface of the semiconductor laser of this example was symmetrical. In contrast, in conventional semiconductor lasers, there is asymmetry in the refractive index distribution between the left and right sides of the mesa, resulting in a near-field image that is asymmetrical.

FIG. 2 is a sectional view showing a second embodiment of the semiconductor laser of the present invention, and the manufacturing process is the same as that of the first embodiment until the striped mesa structure is formed. After the formation of this striped mesa structure, the 5i02 mask was removed and a second growth was performed by low pressure MOVPE to form a p-type GaAs layer 7. Finally, both p and n electrodes (not shown) were formed, the cavity was cleaved to a length of 300 μm, and the chips were separated into individual chips.

This second embodiment uses a current blocking mechanism as p-n-p-n.
From those using junctions, p-type Ga is formed in areas other than the mesa.
As layer and p-type (klo, sGa(14)o, sIn
This is the same as the first embodiment except that the CLsP layer is directly bonded and the hole flow stops due to the energy spike generated in the valence band due to the large band discontinuity between these two layers. The oscillation characteristics are also the first
It was equivalent to the example of .

In the embodiments described above, the active layer is made of Ga005I no
, 5 P s cladding layer (Alo, s Ga(1,4
) o, s I no, s P 1 The active layer composition may be a composition, material, or quantum well that satisfies the oscillation wavelength requirements of the semiconductor laser to be manufactured, and the cladding layer composition depends on the active layer composition used. It is only necessary to select a composition and material that can sufficiently confine light and carriers. Furthermore, it is also possible to introduce a layer that improves the SCH structure or the like depending on the characteristics required of a semiconductor laser. In addition, in the embodiment described above, 1 from the (100) plane to the [011] direction.
Although a GaAs substrate with a (511) B plane tilted by 5.8° was used, this angle may also be within the specified range of the present invention.

〔Effect of the invention〕

As described above, the present invention provides an Al material with a transverse mode control structure that prevents deterioration of laser beam quality while keeping the oscillation wavelength short.
A GaInP semiconductor laser can be provided.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention, FIG. 2 is a sectional view showing a second embodiment, and FIG. 3 is a sectional view showing an example of a conventional semiconductor laser. In the figure, 1- (sll)s fin type GaAa substrate, 2-...
...n type (kl 6.@Ga 6,4) 6.5
In (L5 F cladding layer, 3--GaInP active layer, 4 ''''''' I) type (nilo, a Ga(1
, 4) cLs I no, sP cladding layer, 5...
...p-type layer aInP layer, 6...n-type GaAs
layer,?・---P-type GaAs, 8・”-(51
1) It is a ^-plane n-type GaAs substrate. Agent: Susumu Uchihara, VP type (EaAs layered sword diagram)

Claims (1)

[Claims] The plane orientation is ±1 from the (100) plane in the [01@1@] direction.
On a first conductivity type GaAs substrate tilted by 0° or more and ±30° or less, there is an active layer made of GaInP or AlGaInP or a quantum well layer thereof, and a layer made of AlGaInP with a refractive index smaller than that of the active layer sandwiching this active layer. A double heterostructure consisting of a cladding layer is formed, and the first cladding layer of the second conductivity type above the active layer is formed by partially thickening the layer thickness [01
1] A semiconductor laser having a stripe-like inverted mesa structure in the direction 1), and having a structure in which the mesa structure is embedded by providing semiconductor layers on at least both sides of the mesa structure.