JPH0378792B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a highly reliable visible light semiconductor laser. Conventional visible light semiconductor lasers are -
As far as we are looking for materials within the framework of group compound semiconductors, there are extremely limited materials, provided that they are lattice matched to a substrate crystal of good quality from the point of view of reliability. Even when using
The highest energy is 5800 Å), and the theoretical limit is to obtain a yellow or orange color.

The present invention provides a green visible light laser that overcomes this limitation. - group semiconductors have a wide band gap and many have a direct transition energy gap, so they have potential importance as visible light semiconductor laser materials, but it is difficult to obtain a substrate crystal with a large area, so it is not practical. Efforts on lasers are lagging behind.

The present invention uses GaAs as a substrate, which has extremely good lattice matching conditions and a large band gap.
Zn Sw Te _1-w (band gap ~ 3eV) is used as carrier and optical confinement layer (Al _x Ga _1-x ) _y In _1-y Pz
As _1-z (approximately the maximum value of the direct transition band gap)
It is possible to obtain a highly reliable short wavelength visible light semiconductor laser with a carrier emission layer of 2.2eV).

_The principle of the present invention _{is to} form an ultra _{- thin} film ( _Al When used as a carrier confinement layer by sandwiching it from both sides with _w , the quantized energy level of carriers in the active layer increases as the active layer thickness decreases, up to a maximum of approximately
Based on the formation of levels up to 2.8eV.
This energy increment is shown in FIG. Therefore, by controlling the active layer thickness and active layer composition, the emission wavelength in the active layer can be controlled, and a semiconductor laser with any wavelength from infrared to blue (~4400 Å) can be manufactured. becomes possible. In this case, since GaAs is used as the substrate crystal, there is an advantage that a high quality crystal can be stably supplied.

Furthermore, since the epitaxial layer is strictly or very well lattice-matched to the GaAs substrate crystal, the stress acting on the epitaxial film is small, and a highly reliable and long-life semiconductor laser can be expected.

To increase the gain required for oscillation and improve the light confinement efficiency (Al _x Ga _1-x ) _y In _1-y Pz As _1-z
Instead of an active layer consisting of one layer (Al _x Ga _1-x ) _y
It is effective to form a composite layer, which is formed by alternately forming In _1-y Pz As _1-z layers and Zn Sw Te _1-w layers, as the active layer. Next, the present invention will be explained based on examples. Figure 2 shows Zn Sw Te _1-w ′ on a GaAs substrate,
(Al _x Ga _1-x ) _y In _1-y Pz As _1-z ' This is a planar strip type semiconductor laser formed of a composite layer consisting of GaAs and is the most typical embodiment of the present invention.
On an n-type GaAs substrate 1, an n-type Zn layer with a thickness of 2 to 3 μm is deposited.
Sw Te _1-w 2 is grown as a crystal, and an ultra-thin film (Al _x Ga _1-x ) _y In _1-y Pz As _1-z layer 3 with a thickness of about 0.01 μm or less is formed on top of it by molecular beam epitaxial method. do.

Thereafter, after forming a Zn Sw Te _1-w layer 4 with a thickness of 2 to 3 μm, an n-type GaAs substrate layer 5 of about 1 μm is formed, and a diffusion layer 6 of p-type impurity, such as cadmium, is formed in a stripe shape with a width of 5 μm. By doing so, a lateral current confinement structure is formed, and then n-type and p-type
A semiconductor laser is completed by forming ohmic electrodes 7 and 8. As the thickness of the active layer sandwiched by Zn Sw Te _1-w is made thinner, as shown in Figure 1, the energy increases to the active layer forbidden band energy when the active layer thickness is sufficiently thicker than the de Broglie wavelength of the carrier. The increment ΔE is added to shorten the emission wavelength.
Assuming that the forbidden band width of the Zn Sw Te _1-w layer lattice-matched to the GaAs substrate is approximately 3 eV, the energy gap difference with the active layer must be reduced to increase the carrier confinement efficiency.
If it takes about 0.2eV, the oscillation light energy is 2.8eV
Obtain a semiconductor laser with an oscillation wavelength of 4400 Å. In addition, instead of the single layer (Al _x Ga _1-x ) _y In _1-y Pz As _1-z, Zn Sw Te _1-w and (Al _x Ga _1-x ) _y In _1-y Pz As _1- Forming a repeated composite layer with _z improves the gain,
This is useful for reducing the oscillation threshold because the light confinement effect is improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the thickness of the active layer and the increment of emission energy, and FIG. 2 is a diagram showing an embodiment of the present invention. In the figure, 1 is a GaAs substrate, 2 is an n-type Zn Sw Te _1-w
Layer 3 is (Al _x Ga _1-x ) _y In _1-y Pz As _1-z active layer, 4
5 is a p-type Zn Sw Te _1-w layer, 5 is an n-type GaAs layer, 6 is an impurity diffusion layer, and 7 and 8 are electrodes.

Claims (1)

[Claims] 1 Direct transition type (Al _x Ga _1-x ) _y In _1-y P _z As _1-z (0≦x, y, z
≦1) with different conductivities from each other.
A multilayer structure consisting of Zn Sw Te _1-w layers,
A semiconductor laser characterized by being formed on a GaAs substrate with lattice matching. 2 Each has a film thickness around the de Broglie wavelength of the carrier (Al _x Ga _1-x ) _y In _1-y Pz As _1-z and Zn Sw
A multilayer structure consisting of a composite layer consisting of alternating Te _1- w layers sandwiched between Zn Sw Te _1-w layers with different conductivities was formed on a GaAs substrate by lattice matching. A semiconductor laser featuring: