JP2674381B2 - Semiconductor laser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser used as a light source for information processing equipment or optical communication equipment.

[0002]

2. Description of the Related Art Since a semiconductor laser is extremely small and highly productive, it is currently widely used as a light source for various optoelectronic devices such as information processing devices and optical communication devices. Among them, the AlGaInP semiconductor laser having an oscillation wavelength with high visibility is utilized for downsizing the laser beam pointer. The main characteristics required for a practical semiconductor laser mounted on such a general-purpose device are that the oscillation threshold current is low and that stable high-temperature operation can be performed at 40 ° C to 60 ° C. Recently, Kobayashi et al. Reported that the AlGaInP semiconductor laser exhibits an oscillation threshold current of about 40 mA (SPIE International Conference Proceedings, Vol. 898, p. 84, 19).
1988). Also, Katsuyama et al. Reported in Electronics Letters magazine (Vol. 26, p. 1376, 1990) that the semiconductor laser exhibits an oscillation threshold current of 18 mA.

[0003]

When a semiconductor laser is mounted on the laser beam pointer, the volume of the battery that drives the semiconductor laser occupies most of the volume of the pointer. Therefore, in order to further miniaturize the pointer, it is necessary to reduce the oscillation threshold current of the semiconductor laser and reduce the power consumption.

[0004]

One of the semiconductor lasers of the present invention is a semiconductor substrate having a (0, 0, 1) plane, and [-
An active layer including at least a compound semiconductor layer having an ordered state in the [1,1,1] or [1, -1,1] direction;
And a laser resonator formed in the [1,1,0] direction. From the (0,0,1) plane [1,1,
A semiconductor substrate having a surface slightly inclined in any direction such as the [0] direction, the [1,0,0] direction, and the [0,1,0] direction may be used.

Another semiconductor laser of the present invention is a semiconductor having a plane inclined from the (0,0,1) plane to the [-1,1,0] direction or the [1, -1,0] direction. A substrate, an active layer including at least a compound semiconductor layer having an ordered state in the [-1,1,1] or [1, -1,1] direction, and a laser formed in the [-1,1,0] direction. And a resonator.

[0006]

The group of Gomei et al. (Physical Review Letters, Vol. 60, page 2645, 1988) and other groups are GaInP layer, AlGaInP layer, InGaAs.
It is reported that the epitaxial layer such as the layer and the InGaAsP layer has an ordered state. However, whether or not these semiconductor layers have an ordered state depends on the epitaxial growth conditions. In the case of GaInP, Gomei et al. Reported that the ordered state was formed when the crystal was grown at a group V / group III feed material ratio of 100 or higher or at a crystal growth temperature of 700 ° C. or lower (Applied Physics Letters). Vol. 50, 6
73, 1987). Ga _0.50 In with an ordered state
_In the case of _0.50 P, the Ga atom sublattice and the In atom sublattice are alternately and regularly arranged in the [-1,1,1] or [1, -1,1] direction. Muscarenhus et al. [-1, 1,
1] The electrical vector of light that causes radiative recombination between ground levels in a semiconductor layer having the ordered state is (-1, 1, 1)
It was reported that it was biased in the plane (Physical Review Letters, Vol. 63, page 2108, 1989). Therefore, [-1,
The electric vector of recombination light generated in the semiconductor layer having an ordered state in the [1,1] or [1, -1,1] direction is (-
Biased to the (1,1,1) plane or the (1, -1,1) plane.

In one of the semiconductor lasers of the present invention, the plane orientation of the semiconductor substrate is the (0,0,1) plane. The laser resonator is formed in the [-1,1,0] direction. At this time, the electric vector direction of the TE mode oscillation light of the semiconductor laser is the [1,1,0] direction. The electric vector azimuth is included in the (-1,1,1) plane and the (1, -1,1) plane described above. Therefore, in the semiconductor laser, (-1, 1, 1)
Of the recombined light having the electric vector uniformly distributed in the plane or in the (1, -1,1) plane direction, the recombined light having the electric vector in the [1,1,0] direction contributes to the laser oscillation. On the other hand, in the conventional semiconductor laser having no ordered state, the electric vector of recombination light is uniformly distributed in the three-dimensional direction, and among them, only the recombination light having the electric vector in the [1,1,0] direction is Contributes to laser oscillation. As a result of the above operation, the recombination of the semiconductor laser of the present invention gives gain to the oscillation mode more efficiently than before, and the semiconductor laser exhibits a lower oscillation threshold current. As is clear from the above operation, in the semiconductor laser, the TE
Since the emission of light to the mode is promoted, it is characterized in that the effect of suppressing the TM mode oscillation is high and that the TM mode spontaneous emission light is less mixed into the laser oscillation light.

According to another semiconductor laser of the present invention,
A semiconductor substrate having a surface inclined from (0,0,1) in the [-1,1,0] direction (or [1, -1,0] direction) is used. The orientation of the ordered state of the epitaxial layer on the semiconductor substrate having the (0,0,1) plane is [-1,1,
1] direction and [1, -1,1] direction are mixed equally, while (0,0,1) to [-1,1,0] direction (or [1, -1,0] It is known that the orientation of the ordered state is biased in the [-1,1,1] direction ([1, -1,1,] direction) on a semiconductor substrate having a surface inclined in the [] direction (Japanese Journal). Journal of Applied Physics Vol. 28, L1728, 1989, and 1991 Spring Conference on Applied Physics, Lecture 32a-ZG-
5). That is, the order degree of the ordered state of the epitaxial layer on the tilted substrate is higher. Therefore, the operation of the present invention described above works more strongly. Even when the inclined substrate is used, the electric vector direction of the recombined light is still (-1, 1, 1,
1) plane (or (1, -1,1) plane). The laser cavity direction is from [-1,1,0] direction to [0,0,
Although tilted in the [1] direction, the electric vector direction of the TE mode oscillation light is still kept in the [1,1,0] direction. Therefore, when the above-mentioned tilted substrate is used, the recombination photoelectric vector direction and T
The geometrical relationship between the E-mode oscillating opto-electrical vector orientations is kept exactly the same as for the (0,0,1) substrate.

[0009]

FIG. 1 shows one embodiment of the semiconductor laser of the present invention. First, on a semiconductor substrate 2 made of Si-doped n-type GaAs, a 1.2 μm thick Si-doped n-type (Al
_{0. 7} Ga _{0.3) 0.5} In clad layer 3 of _0.5 P,
80 nm thick undoped (Al _0.10 Ga _0.90 ) _0.50 I
An active layer 4 made of n _0.50 P and a cladding layer 5 made of Zn-doped p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P having a thickness of 1.2 μm were epitaxially grown. In in the active layer
It is also possible to use an _x Ga _1-x As _1-y P _y layer.
Further, an In _1-x Ga _x As _y P _1-y layer may be used for the active layer, in which case InP is used for the semiconductor substrate 2, the cladding layer 3 and the cladding layer 5. Although the above-mentioned active layer is composed of a simple single-composition layer, a well-known multi-quantum well active layer can also be formed. In this case, an ordered state may be formed in the quantum well layer that will be the recombination emission layer.

The plane orientation of the semiconductor substrate 2 is (0,0,1)
Is a surface inclined by 6 degrees in the [-1,1,0] direction. To form an ordered state with high order in the active layer, 1
A tilt angle of 0 degrees or less is suitable. The plane orientation of the semiconductor substrate 2 may be the (0,0,1) plane. Further, from the (0,0,1) plane, [1,1,0] direction, [1,0,0] direction, [0,
The semiconductor substrate 2 having a surface inclined by 1 to 3 degrees in an arbitrary direction such as the [1,0] direction may be used. As is well known, such a semiconductor substrate has an effect of improving the morphology of an epitaxial crystal.

Epitaxial growth was performed by the low pressure metal organic crystal growth method (MOVPE method). In this example, the crystal growth temperature was 660 ° C. and the group V / group III feed material ratio was 200. In order to form an ordered state with a high degree of order, the crystal growth temperature is 700 ° C. or lower, and the V / III supply flow rate ratio is 10
0 or more is suitable. Since these crystal growth conditions are conditions for forming an ordered state having the effect of the present invention, the crystal growth conditions of other layers such as the cladding layer may be different. Growth rate is about 1.8 μm / h
r. Trimethyl aluminum (TM
A), triethyl gallium (TEG), trimethyl an indium (TMI), dimethyl zinc (DMZ), phosphine (PH _3), arsine (AsH _3), was used disilane (Si ₂ H _6). It is also possible to grow using a gas source molecular beam crystal growth method (GSMBE method) or a chemical beam epitaxial method (CBE method).

After the epitaxial growth, stripes 9 were formed on the cladding layer 5 by using the photolithography method. The stripes 9 are oriented in the [-1,1,0] direction. The stripe 9 forms a laser resonator. Strictly speaking, when an inclined substrate is used, the laser resonator direction is inclined from the [-1,1,0] direction to the [0,0,1] direction. After forming the stripes 9, Si-doped n-type G
A block layer 6 made of aAs was selectively grown outside the stripe 9, and a contact layer 7 made of Zn-doped p-type GaAs was further grown on the entire surface. After forming the contact layer 7, the n-side electrode 1 and the p-side electrode 8 were formed.
Finally, the cleavage is performed to make the reflecting mirrors facing each other (-1, 1,
0) surface. The reflecting mirror may be formed by using dry etching instead of cleaving. Further, a vertical emission type semiconductor laser (T. Takamori et al., Applied Physics Letters, Vol. 55, page 1053, 19)
(1989), a reflecting mirror having a surface other than (-1,1,0) or a curved reflecting surface may be used. The semiconductor laser is completed through the above steps. The semiconductor laser is TE
The laser beam 10 oscillates in the mode, and the electric vector direction of the laser beam 10 is the [1,1,0] direction.

[0013]

The semiconductor laser of the present invention has a low threshold and excellent high temperature operation characteristics. Above all, (0,0,1)
The semiconductor laser using the semiconductor substrate tilted 6 degrees in the [-1,1,0] direction from the plane showed a lower threshold current than that using the (0,0,1) semiconductor substrate.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a semiconductor laser of the present invention.

[Explanation of symbols]

 1 Electrode 2 Semiconductor Substrate 3 Cladding Layer 4 Active Layer 5 Cladding Layer 6 Block Layer 7 Contact Layer 8 Electrode 9 Stripe 10 Laser Light

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-67839 (JP, A) JP-A-4-273490 (JP, A) JP-A-63-120492 (JP, A) JP-A-5- 41560 (JP, A) JP 5-29700 (JP, A) JP 4-237183 (JP, A)

Claims (4)

(57) [Claims] 1. A semiconductor substrate having a (0,0,1) plane,
An active layer containing at least a compound semiconductor layer having an ordered state in the [-1,1,1] or [1, -1,1] direction;
A semiconductor laser having a laser resonator formed in the [-1,1,0] direction. 2. From the (0,0,1) plane to [-1,1,0]
Substrate having a plane inclined in the direction of [1, -1,0] or [-1,1,1] or [1, -1,1]
A semiconductor laser comprising an active layer including at least a compound semiconductor layer having an ordered state in a direction, and a laser resonator formed in a [-1,1,0] direction. 3. The semiconductor substrate is made of GaAs and the G
(Al _x Ga _1-x ) _y In _1-y P layer or In as the active layer in the semiconductor multi-layer structure formed on the aAs substrate.
3. The semiconductor laser according to claim 1, wherein an _x Ga _1-x As _1-y P _y layer is provided. 4. The semiconductor substrate is made of GaAs,
The semiconductor laser according to claim 1, wherein an In _1-x Ga _x As _y P _1-y layer is provided as the active layer in a semiconductor multilayer structure formed on an nP substrate.