JPH0510374Y2 - - Google Patents

Description

[Detailed explanation of the idea] (b) Industrial application fields The present invention relates to semiconductor lasers.

(b) Conventional technology Currently, visible light semiconductor lasers are used as light sources for CDs (compact discs), DADs (digital audio discs), VDs (video discs), LBPs (laser beam printers), etc. There is.

As this type of semiconductor laser, Applied
Physics Letter 40(5), 1March 1982, pp372−
There is a VSIS type semiconductor laser disclosed in pp374.

The figure shows such a semiconductor laser, where 1 is a p-type GaAs
2 is a current confinement layer made of n-type GaAs that is laminated on one main surface of the substrate, and a current confinement layer that extends in the direction perpendicular to the plane of the paper approximately in the center of the surface of the current confinement layer and has a depth that reaches the substrate 1. grooves are formed. Reference numeral 3 denotes an oscillation layer laminated on the constriction layer 2, and the oscillation layer is formed by laminating a first cladding layer 4, an active layer 5, and a second cladding layer 6 in this order from the constriction layer side. Further, the first and second cladding layers 4 and 6 and the active layer 5 each have p
Type Ga _1-x Al _x As (0<x<1), n-type Ga _1-x Al _x As,
It consists of non-doped Ga _1-y Al _y As (0≦y<1, y<x). 7 is a cap layer laminated on the second cladding layer 6, and the cap layer is made of n-type GaAs.
Consisting of 8 and 9 are ps laminated on the other main surface of the substrate 1 and the cap layer 7, respectively, and are in ohmic contact.
They are an electrode and an n-electrode.

In such a semiconductor laser, when a forward bias is applied between the p-electrode 8 and the n-electrode 9, the current is constricted by the current confinement layer 2 and flows in a limited manner through the oscillation layer 3 directly above the groove. Furthermore, since the first and second cladding layers 4 and 6 have a larger band gap energy and a smaller optical refractive index than the active layer 5,
Electrons and holes are concentrated in the active layer 5 directly above the groove, and a laser beam is generated in the active layer 5, which is output from the resonator end face perpendicular to the extending direction of the groove. Further, in such a configuration, the first cladding layer 4 on the current confinement layer 2 is made thin enough to transmit the laser light generated in the active layer 5, and the current confinement layer 2 is a layer capable of absorbing the laser light. Therefore, an effective refractive index difference occurs between the active layer 5 directly above the groove and the other portion (refractive index waveguide type). Therefore, the laser light can be confined in the horizontal direction in the active layer 5, and the laser light emitted from the active layer 5 has a single longitudinal and transverse mode.

Furthermore, when using a semiconductor laser as a light source for a CD or the like, it is currently proposed to use a semiconductor laser capable of multi-mode oscillation (self-sustained oscillation) in the longitudinal mode, taking into consideration return optical noise.

(c) Problems to be solved by the invention Also in the semiconductor laser shown in the figure, the thickness of the first cladding layer 4 on the current confinement layer 2 is made thicker than in the past, and the laser light in the current confinement layer 2 is increased. Longitudinal multimode oscillation is theoretically possible if the absorption rate is lowered.

However, since the layer thickness adjustment must be controlled with an accuracy of 10 ^-2 μm or less, the currently widely used liquid phase epitaxial growth method has insufficient reproducibility in manufacturing.

(d) Means for solving the problems The present invention was made in view of the above points, and its structural features include a substrate made of p-type or n-type GaAs with grooves formed on one main surface; Laminated on one main surface of the substrate, p-type or n-type with a flat surface
A first cladding layer made of Ga _1-x Al _x As (0<x<1), laminated on the cladding layer and non-doped.
An active layer consisting of Ga _1-y Al _y As (0≦y<1, y<x), which is laminated on the active layer and is n-type or p-type
The second layer consisting of Ga _1-z Al _z As (1<z<0, z>y)
In a semiconductor laser equipped with a cladding layer, the thickness of the first cladding layer at a portion other than directly above the groove is 0.24 to 0.35 μm, and the first cladding layer and the second cladding layer have a thickness of 0.24 to 0.35 μm.
The Al composition ratio of the cladding layer is increased by 0.01 to 0.03 compared to the Al composition ratio of the second cladding layer, and the oscillated laser beam has a single transverse mode and multiple longitudinal modes.

(e) Effect In such a semiconductor laser, multimode oscillation occurs with a probability of over 80%.

(f) Example As an example of the present invention, in the semiconductor laser shown in FIG. 1, the layer thickness of the first cladding layer 4 on the current confinement layer 2 is set to 0.25 μm, and The active layer 5 and the second cladding layer 6 may have Al composition ratios x, y, and z of 0.445, 0.15, and 0.430, respectively.

It should be noted that if the first and second cladding layers 4 and 6 are
The Al composition ratio is the Ga and AlAs in each growth melt.
The ratio may be set to 1g: 1.55mg and 1g: 1.45mg.

In the device of this embodiment, when manufactured by the liquid phase epitaxial growth method, there is a probability of more than 90% that the transverse mode will be single and the longitudinal mode will be multiple.

According to experiments, when the layer thickness of the first cladding layer 4 on the current confinement layer 2 is set to 0.24 to 0.35 μm, the difference in Al composition ratio between the first cladding layer 4 and the second cladding layer 6 is It has been found that if the value is 0.01 to 0.03, a semiconductor laser having a single transverse mode and multiple longitudinal modes can be obtained with a probability of 80% or more even when manufactured by liquid phase epitaxial growth. Also, above
When the difference in Al composition ratio is 0.01 to 0.03, if the thickness of the first cladding layer 4 on the current confinement layer 2 is less than 0.24 μm, the longitudinal mode will be single, and if it is 0.5 μm or more, the transverse mode will be multiple. It was found that the transverse mode is single and the longitudinal mode is multiple only when the thickness is 0.24 to 0.5 μm. Furthermore, the above layer thickness is 0.35μm
It was found that when the thickness is 0.5 μm or less, the gain waveguide type is used, and the oscillation threshold current increases.

Therefore, the present invention is not limited to the above-described embodiment, and the thickness of the first cladding layer 4 on the current confinement layer 2 is 0.24 to 0.35 μm, and the thickness of the first cladding layer 4 and the second cladding layer 6 are 0.24 to 0.35 μm. It is sufficient if the difference in Al composition ratio is 0.01 to 0.03.

(g) Effects of the invention In manufacturing the semiconductor laser of the invention, the thickness of the first cladding layer only needs to be controlled with an accuracy of 10 ^-2 μm or more, so the liquid phase epitaxial growth method is used. It can be mass-produced with good reproducibility even when

[Brief explanation of the drawing]

The figure is a sectional view showing a semiconductor laser to which the present invention is applied. 1...Substrate, 4...First cladding layer, 6... Second cladding layer.

Claims (1)

[Claims for Utility Model Registration] P-type or n-type GaAs with grooves formed on one main surface
A substrate consisting of p-type or n-type Ga _1-x Al _x As (0<x
A first cladding layer consisting of <1) is laminated on the cladding layer and is non-doped Ga _1-y Al _y As (0≦y<
1, y<x), an active layer laminated on the active layer and consisting of n-type or p-type Ga _1-z Al _z As (0<z<1,
z>y), the thickness of the first cladding layer in a portion excluding the area directly above the groove is 0.24 to 0.35 μm, and the Al composition ratio of the first cladding layer is 0.24 to 0.35 μm. A semiconductor laser characterized in that the Al composition ratio is 0.01 to 0.03 greater than the Al composition ratio of the second cladding layer, and the laser beam oscillated has a single transverse mode and multiple longitudinal modes.