JP2973215B2 - Semiconductor laser device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an AlGaInP-based semiconductor laser device that oscillates in a single transverse mode.

(Prior Art) Recently, AlGa oscillated in a single transverse mode formed by crystal growth by metal organic pyrolysis (hereinafter abbreviated as MOVPE).
As an InP-based semiconductor laser device, a structure as shown in FIG. 3 has been reported (Preliminary Proceedings of the 50th Annual Meeting of the Japan Society of Applied Physics, Third Volume p893 28a-ZG-4). In manufacturing this structure, the n-type GaAs substrate 1
On the n-type (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P cladding layer 2, Ga
InP active layer 3, P-type (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P cladding layer 4, p-type Ga _0.5 In _0.5 P layer 8, p-type GaAs contact layer 9
Are sequentially formed. Next, by photolithography,
A mesa stripe is formed using O as a mask. And S
With the iO mask attached, the second growth is performed and the etched portion is buried with an Al _0.5 In _0.5 P layer 11 and an n-type GaAs layer 12. Next, the SiO mask is removed, and p and n electrodes are formed and processed into a laser chip.

With this structure, the current is Al _0.5 In _0.5 P layer 11, n-type GaAs layer
Blocked by 12 and injected only into the mesa stripes. Also, at the time of etching for forming the mesa stripe,
Since the thickness of the p-type cladding layer 4 other than the mesa stripe portion is etched to a thickness insufficient for confining light, Al
In parts of the _0.5 an In _0.5 P layer 11, the Al _0.5 In _0.5 P layer 11
Then, the light is reflected, and there is a difference in the actual refractive index in the lateral direction, so that the light is guided only to the mesa stripe portion. Thus, in this structure, the current confinement mechanism and the optical waveguide mechanism are simultaneously created,
Since it is a real refractive index guided laser, astigmatism is also small.

(Problem to be Solved by the Invention) In the structure of FIG. 3 described above, the electrode is formed by limiting the number of times of growth to two times. However, according to this method, the contact area between the P-type contact layer and the electrode is small, and It is difficult to obtain good electrical characteristics with good reproducibility. In order to prevent this problem, there is a structure in which the number of times of growth is increased once and a P-type contact layer is grown on the entire surface to form a full-surface electrode, but this increases the number of times of growth and becomes complicated. In the conventional manufacturing method, Al _0.5 In _0.5
Although the P layer is selectively grown using a dielectric film as a mask, a mixed crystal system containing Al is easily deposited on the dielectric film, and it is difficult to establish an appropriate growth technique. As described above, the conventional semiconductor laser device has a problem to be solved.

An object of the present invention is to provide an AlGaInP-based semiconductor laser device which solves the above-described problems, can be manufactured easily, and has a lateral mode control structure with small astigmatism.

(Means for Solving the Problems) The semiconductor laser device of the present invention comprises a Ga laser
An active layer composed of InP or AlGaInP or a quantum well layer thereof, and a smaller refractive index than the active layer sandwiching the active layer.
A double heterostructure composed of a cladding layer made of AlGaInP is formed, and the cladding layer above the active layer is made of p-type (Al _X Ga _1-X ) _0.5 In _0.5 P, and the upper cladding layer is made of It has a stripe-shaped mesa structure formed by partially increasing the layer thickness, and has a p-type GaInP layer on the upper surface of the mesa structure.
GaAs layer whose quantum level is larger than the energy gap of the active layer in the portion other than the upper surface of the p-type GaInP layer, and p-type (Al _Y Ga _1-Y ) _0.5 In _0.5 P
(Y> X) layer.

(Operation) According to the structure of the present invention, the portion other than the upper surface of the mesa structure has a GaAs layer whose quantum level is larger than the energy gap of the active layer. The p-type (Al _X Ga _1-X ) _0.5 In _0.5 P cladding layer and the p-type (Al _Y Ga _1-Y ) _0.5 In _0.5 P (Y> X) layer sandwiching the GaAs layer The carrier depletion layer due to large band discontinuity expands,
Even if the element is biased, the voltage is p-type (Al _X Ga _1-X )
_{The 0.5} In _0.5 P is applied to the depletion layer in the cladding layer, so that holes cannot flow and functions as a current blocking layer.
On the other hand, in the mesa portion, there is a p _- type GaInP layer between the p-type (Al _X Ga _1-x ) _0.5 In _0.5 P cladding layer and the GaAs layer, so that band discontinuity is reduced and holes flow through this portion. Can be. In this way, current is injected only into the mesa portion. Also, the GaAs layer cannot absorb light from the active layer because the quantum level is defined as a thickness that is larger than the energy gap of the active layer. And the p-type (Al _Y G
a _1-Y ) _0.5 In _0.5 P (Y> X) layer is p-type (Al _X Ga _1-X ) _0.5 I
Since the refractive index is smaller than that of the n _0.5 P cladding layer, a real refractive index type waveguide mechanism that does not use light absorption is provided, and astigmatism can be suppressed to a small value. With this structure, the entire surface electrode can be formed with a small number of growth times of two, and good electrical characteristics can be easily obtained.

(Example) An example of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of a semiconductor laser device according to the present invention, and FIG. 2 is a process diagram thereof. Figure 1
The laser chip of the example is cut along a plane perpendicular to the resonator axis.

In the production of this embodiment, first, the first decompression MOVPE
N-type GaAs substrate 1 (Si-doped; n = 2 × 10 ¹⁸⁾
cm ⁻³ ), an n-type (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P cladding layer 2 (n = 5 × 10 ¹⁷ cm ⁻³ ; thickness 1 μm), a Ga _0.5 In _0.5 P active layer 3 (undoped; thickness 1 μm) ), P-type (Al _0.6 G
a _0.4 ) _0.5 In _0.5 P clad layer 4 (p = 5 × 10 ¹⁷ cm ⁻³ ; thickness 1.0 μm) and a p-type Ga _0.5 In _0.5 P cap layer 5 were sequentially grown (FIG. 2A). The growth conditions are temperature 700 ℃,
Pressure 70 Torr, V / III = 200, total flow rate of carrier gas (H ₂ )
It was 151 / min. As raw materials, trimethyl indium (TMI: (CH ₃ ) ₃ In), triethyl gallium (TEG: (C
₂ H _{5) 3} Ga), trimethyl aluminum _{(TMA: (CH 3) 3} A
l), arsine (AsH ₃ ), phosphine (PH ₃ ), n-type dopant: hydrogen selenide (H ₂ Se), p-type dopant: cyclopentadienyl magnesium (Cp ₂ Mg). Photolithography is applied to the wafer thus grown to a width of 4
A μm sweep-shaped SiO ₂ mask 10 was formed (FIG. 2 (b)). Next, using the SiO ₂ mask 10, a p-type (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P
A part of the cladding layer 4 (here, 0.8 μm) was etched in a mesa shape (FIG. 2C). Next, SiO ₂
The mask was removed (FIG. 2 (d)). And decompression MOVPE
For the second growth, and the p-type GaAs layer 6 and the p-type (Al
_0.6 Ga _0.2 ) _0.5 In _0.5 P cap layer 7 (p = 5 × 10 ¹⁷ c
m ^-3 ; thickness 1.0 μm), p-type Ga _0.5 In _0.5 P layer 8, p-type GaAs
A contact layer 9 was formed (FIG. 2E). Finally
Form both p and n electrodes and cleave to 300 μm cavity length,
Separated into individual chips.

The astigmatism of the semiconductor laser device of the present invention thus obtained is 4 μm or less. Further, as can be seen from the above-described manufacturing process, the number of times of growth for obtaining the laser device having good characteristics is two times, and the entire surface electrode can be formed.

In the above-described embodiments, the composition of the active layer and the cladding layer is specified. However, the composition of the active layer may be a composition or a quantum well that satisfies the oscillation wavelength requirement required for the laser device to be manufactured. A composition that can sufficiently confine light and carriers with respect to the composition of the active layer to be used may be selected. Further, the cladding layer can be made more multilayer, for example, by using a SCH structure depending on the characteristics required for the laser device.

(Effect of the Invention) As described above, according to the present invention, a semiconductor laser device having small astigmatism can be manufactured in a self-aligned manner with a small number of manufacturing steps.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIGS.
(E) is a sectional view showing a production process of the embodiment, and FIG. 3 is a sectional view showing an example of a conventional semiconductor laser device. 1... N-type GaAs substrate, 2... N-type (Al _0.6 Ga _0.4 ) _0.5 In
_0.5 P clad layer, 3 ... Ga _0.5 In _0.5 P active layer, 4 ...
p-type (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P clad layer, 5 ... p-type
Ga _0.5 In _0.5 P cap layer, 6 ...... p-type GaAs layer, 7 ...... p
Type (Al _0.8 Ga _0.2 ) _0.5 In _0.5 P cap layer, 8 ... p-type Ga
_0.5 In _0.5 P layer, 9 ... p-type GaAs contact layer, 10 ... Si
O ₂ film, 11... Al _0.5 Ga _0.5 P layer, 12... N-type GaAs layer.

Claims (1)

(57) [Claims] 1. An n-type GaAs substrate on which GaInP or AlGaInP
Alternatively, a double hetero structure composed of an active layer made of the quantum well layer and a clad layer made of AlGaInP having a smaller refractive index than the active layer sandwiching the active layer is formed, and the clad above the active layer is formed. Layer is p-type (Al _X Ga _1-X )
Becomes at _0.5 an In _0.5 P, the upper clad layer has a stripe-shaped mesa structure formed by the layer thickness becomes thicker partially has a p-type GaInP layer on the upper surface of the mesa structure, these On the entire upper surface of the structure, there is provided a GaAs layer whose quantum level is larger than the energy gap of the active layer in a portion other than the upper surface of the p-type GaInP layer. _Y Ga _1-Y ) _0.5 In _0.5 P
A semiconductor laser device having a (Y> X) layer.