JP2758597B2 - 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, AlGas oscillating 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 (Extended Abstrarts of the 18th Edition).
th Conference on Solid State Devices and Material
s, Tokyo, 1986, pp.153-156). In this structure, an n-type (Al _0.5 Ga _0.5 ) _0.51 In
_0.49 P cladding layer 2, GaInP active layer 3, p-type (Al _0.5 Ga
_0.5 ) _0.51 In _{0.49 A} P cladding layer 4 and a p-type GaAs cap layer 7 are sequentially formed. Then SiO ₂ by photolithography
Is used as a mask to form a mesa stripe. And
The second growth is performed with the SiO ₂ mask attached and the etched portion is buried with an n-type GaAs layer 8. Next, SiO ₂
The mask is removed, and the p-type GaAs contact layer 9 is grown in the third growth so that an electrode can be formed on the entire surface of the p-type. With this structure, the current is blocked by the n-type GaAs layer 8 and injected only into the mesa stripe portion. Further, at the time of etching for the formation of the mesa stripe, the thickness of the p-type cladding layer other than the mesa stripe portion is etched to a thickness that is insufficient for trapping light. Light is absorbed by the type GaAs layer 8, and light is guided only to the mesa stripe portion. Thus, in this structure,
A current confinement mechanism and an optical waveguide mechanism are simultaneously created. (Problem to be Solved by the Invention) In the above-described structure, the etching at the time of forming the mesa stripe for determining the distance between the active layer 3 and the n-type GaAs layer 8 is time-controlled etching. For this reason, the controllability and reproducibility of the thickness of the p-type clad layer after etching are poor, and there is a problem in that the variation in characteristics between element lots is large. An object of the present invention is to provide a semiconductor laser device that solves this problem. (Means for Solving the Problems) According to the present invention, on a GaAs substrate of the first conductivity type, lattice matching (Al _x Ga _1-x ) _w In _1-w P (0 ≦ x ≦ 0.3, W ~ 0.5
The active layer consisting of 1) and the active layer sandwiched between (Al _y Ga _1-y ) _w
A double heterostructure formed by a cladding layer made of In _1-w P (x + 0.4 ≦ y) is provided, and both sides (Al _y Ga _1-y ) are formed on the second conductivity type cladding layer opposite to the substrate. The quantum level when sandwiched between _w In _1-w P is the second conductivity type (Al _z Ga) with a thickness that does not absorb the emitted light compared to the oscillation energy of the active layer.
_1-z ) _w In _1-w P (z ≦ y−0.4) layer and a mesa stripe-shaped second conductivity type (Al _y Ga _1-y ) _w In _1-w provided on this layer
A GaAs layer of the first conductivity type is provided on a portion other than the P cladding layer and the mesa stripe cladding layer. (Operation) When the above-described configuration of the present invention is used, the current confinement has the same mechanism as that of the conventional structure, and the optical waveguide is sandwiched by p-type (Al _y Ga _1-y ) _w In _1-w P. (Al _z Ga _1-z ) _w In _1-w P
If the layer has a composition that absorbs light emitted from the active layer in bulk,
In the present invention, the level of the film is quantized, and the quantum level is specified to be a thickness that is larger than the oscillation energy of the active layer. And the transverse mode is controlled by the same mechanism as that of the conventional structure. Also, (Al _x Ga _1-x ) _w In _1-w P (W ~
0.51) If there is a difference of x of 0.4 or more in the mixed crystal, a hydrochloric acid-based etchant can etch a crystal having a large x composition more than 30 times faster than a crystal having a small x composition. For this reason, in the manufacturing process of this structure, when forming the mesa stripe,
Etching of the p-type cladding at locations other than the mesa stripe portion can be stopped between the upper and lower p-type cladding layers with a considerable time width. For this reason, if a growth method excellent in film thickness controllability such as MOVPE is used, an element having a small variation in characteristics between lots can be obtained with good reproducibility. (Example) Hereinafter, an example of the present invention will be described with reference to the drawings. First
FIG. 1 is a sectional view of a semiconductor laser device according to an embodiment of the present invention, and FIG. 2 is a manufacturing process diagram of the semiconductor laser device. First, in the first growth, the n-type GaAs substrate 1 (S: doped, n
= 2 × 10 ¹⁸ cm ⁻³ ) and n-type (Al _0.5 Ga _0.5 ) _0.51 In _0.49
P cladding layer 2 (n = 1 × 10 ¹⁸ cm ⁻³ ; thickness 1.2 μm), Ga
InP active layer 3 (undoped; thickness 0.1 μm), lower p-type (Al _0.5 Ga _0.5 ) _0.51 In _0.49 P clad layer 4 (p = 5 × 10
¹⁷ cm ^-3 ; thickness 0.3 μm), p-type GaInP layer 5 (p = 1 × 10 ¹⁸ c
m ^-3 40 Å), upper p-type _{(Al 0.5 Ga 0.5) 0.51 In} 0.49 P cladding layer ^{6 (p = 5 × 10 17} cm -3; thickness 1 [mu] m), p-type GaAs
The cap layer 7 (p = 2 × 10 ¹⁸ cm ⁻³ ; thickness 0.5 μm) was sequentially grown (FIG. 2A). For growth, reduced pressure MOVPE
The growth conditions were as follows: temperature 700 ° C, pressure 70 Torr, V / III =
The total flow rate of 200 and carrier gas (Hz) was set to 15 (l / min).
Raw materials include trimethylindium (TMI: (CH ₃ ) ₃ In), triethyl gallium (TEG: (C ₂ H ₅ ) ₃ Ga), trimethyl aluminum (TMA: (CH ₃ ) ₃ Al), arsine (AsH ₃ ), Phosphine (PH ₃ ), p-type dopant: dimethyl zinc (DM
Z: (CH ₃ ) ₂ Zn), n-type dopant: hydrogen selenide (H ₂ S
e) was used. A stripe-shaped SiO ₂ mask 10 was formed on the thus grown wear by photolithography (FIG. 2B). Next, the p-type GaAs cap layer 7 was etched into a mesa using a phosphoric acid-based etchant using this SiO ₂ 10. Then, (Al _0.5 Ga _0.5 ) _0.51 In _0.49 P
The upper p-type (Al _0.5 Ga _0.5 ) _0.51 In _0.49 P clad layer 6 was etched into a mesa shape using a hydrochloric acid-based etchant having an etching rate of 6000 ° / min for Al and an etching rate of 50 ° / min for GaInP (second). Figure (c).
Then, the _second growth was performed by MOVPE with the SiO ₂ mask 10 attached, and the n-type GaAs layer 8 was grown (FIG. 2 (d)). Next, the SiO ₂ mask 10 is removed by etching (FIG. 2E), and a third growth is performed by MOVPE to form a p-type G
An aAs contact layer 9 was grown (FIG. 2 (f)). The second and third growth conditions are the same as the first growth described above. Finally, both p and n electrodes are formed, and the capacity length is 250 μm
And cleaved into individual chips. Table 1 shows the average value of the maximum light output in the fundamental transverse mode oscillation of the three laser wafer lots of the present invention manufactured by the above-described method and the three laser wafer lots obtained by the conventional method (30 pieces for each lot). As can be seen from Table 1, when the present invention is used, the distance between the active layer and the GaAs layer that absorbs light can be set as designed, and variations in characteristics between lots can be suppressed. In the above-described embodiment, the active layer is GaInP and the cladding layer is (Al _0.5 Ga _0.5 ) _0.51 In _0.49 P. However, in order to change the oscillation wavelength (to make the wavelength shorter), the range satisfying the requirements of the present invention is used. What is necessary is just to increase Al composition of an active layer. In the embodiment,
Although the three cladding layers have the same composition, they may be changed according to the characteristics required for the laser. (Effect of the Invention) As described above, according to the present invention, it is possible to obtain a fundamental lateral mode control AlGaInP-based semiconductor laser device having small variations in characteristics between growth lots.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 (a).
To (f) are cross-sectional views showing the manufacturing process of the present invention, and FIG.
FIG. 11 is a cross-sectional view illustrating an example of a conventional semiconductor laser device. In the figure, 1 is an n-type GaAs substrate, 2 is an n-type (Al _0.5 Ga _0.5 )
_0.51 In _0.49 P cladding layer, 3 is GaInP active layer, 4 is lower p-type (Al _0.5 Ga _0.5 ) _0.51 In _0.49 P cladding layer, 5 is p-type
GaInP layer, 6 is the p-type (Al _0.5 Ga _0.5 ) _0.51 In _0.49 P cladding layer, 7 is the p-type GaAs cap layer, 8 is the n-type GaAs layer,
9 is a p-type GaAs contact layer, and 10 is a SiO ₂ mask.

Continuation of the front page (56) References JP-A-63-43387 (JP, A) JP-A-62-200785 (JP, A) JP-A-61-77384 (JP, A) Appl. Phys. Vol. 61, No. 5, 1 March 1987, PP. 1714-1719 (58) Field surveyed (Int.Cl. ⁶ , DB name) H01S 3/18-3/19

Claims (1)

(57) [Claims] An active layer made of (Al _x Ga _{1 -x} ) _w In _{1 -w} P (0 ≦ x ≦ 0.3, w to 0.51) lattice-matched to the first conductivity type GaAs substrate, and the active layer Sandwich (Al _y Ga _1-y ) _w In _1-w P (x
+ 0.4 ≦ y), a double heterostructure formed by a cladding layer composed of (Al _y Ga _1-y ) _w In _1-w P is provided on the second conductivity type cladding layer opposite to the substrate. The second conductive type (Al _z Ga _1-z ) _w In _{1-w has a} thickness at which the quantum level when sandwiched between the layers does not absorb the emitted light compared with the oscillation energy of the active layer.
A P (z ≦ y−0.4) layer, a mesa-stripe-shaped second conductivity type (Al _y Ga _1-y ) _w In _1-w P clad layer provided on this layer, and a mesa-stripe clad A semiconductor laser device comprising a first conductivity type GaAs layer provided in a portion other than the layer.