JPH02209781A - Superlattice semiconductor laser - Google Patents

Abstract

PURPOSE:To move energy of a current from an electron implanted layer of an N-type semiconductor to a quantum wall active layer by providing the electron implanted layer made of quantum well or a superlattice layer having conduction band base quantum level energy resonant with conduction band high order subband quantum level energy of semiconductor. CONSTITUTION:A superlattice or quantum well structure is used as part or all of an active layer and a clad layer, conduction band high order subband level (e.g. n=2 quantum level) energy of semiconductor for forming the active layer coincides with conduction band base quantum level (n=1) energy of semiconductor for composing a clad layer to form a resonance level. The active layer is doped in P-type, and holes are always in the active layer. Thus, since the electron implanted layer made of the quantum well or superlattice having conduction band base quantum level energy resonator the conduction band high order subband level energy of semiconductor for composing P-type doped quantum well or superlattice active layer is provided, electrons can be implanted at a high speed efficiently to the active layer and the holes exist in the active layer. Accordingly, light emitting response can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a superlattice semiconductor laser, and particularly to improving its performance.

[Conventional technology]

FIG. 2 (al is a diagram showing the structure of a conventional double heterojunction semiconductor laser; in the figure, 8 and l are n-side electrodes, 2 is an n-type (hereinafter referred to as n-) ohmic layer, and 3 is an n-side electrode). - cladding layer, 5' is an active layer, 7 is a p-type (hereinafter referred to as p-) cladding layer, 8 is a p-ohmic layer, and 9 is a p-side electrode.

In addition, Figure 2 (bl is shown in "Laser and Optical Communication" (written by Aratabe Uda, Maruzen, 1973, p. 85),
2 is a diagram showing a potential diagram of the active layer and ground layer portions of the semiconductor laser having the structure shown in a), in which 10 is a conduction band, 11 is a valence band, 12 is an electron,
13 is a hole, and 14 is a laser beam.

In this conventional semiconductor laser device, the energy gap is larger than the energy gap E of the semiconductor constituting the active layer 5', and the energy gap E':< E:) constitutes the cladding layer 3.7. At this time, the carriers (electrons and holes) injected from the cladding layer 3.7 are initially at the bottom of the conduction band (electrons) of the cladding layer semiconductor.
, occupies the top of the valence band (holes). An inelastic scattering process is required for these carriers to move into the active layer semiconductor and occupy the conduction band bottom (electrons) and valence band top (regular tag) of the active layer semiconductor, which has an energy gap smaller than that of the cladding layer. extra energy (E@-E,
), and this energy relaxation process (usually caused by longitudinal optical phonon and acoustic phonon scattering) is the fundamental cause of reducing the luminescence recombination quantum efficiency and luminescence response speed in the active layer.

Furthermore, even in the case of a quantum well active layer in which the thickness of the active layer is about the de Broglie wavelength (several hundred angstroms), the performance of laser light emission deteriorates due to a similar energy relaxation process.

[Problem to be solved by the invention]

Since the conventional superlattice semiconductor laser is configured as described above, there have been problems of low emission recombination efficiency and slow emission response speed.

This invention was made to solve the above-mentioned problems, and provides a superlattice semiconductor laser that can transfer electron energy from the electron injection layer on the n-type semiconductor side to the quantum well active layer with high efficiency. The purpose is to

[Means to solve the problem]

The superlattice semiconductor laser according to the present invention uses a superlattice or quantum well structure in part or all of the active layer and the cladding layer, and has a conduction band higher-order subband level (for example, n = 21 child level) energy is the conduction band base quantum level (n =
1) The active layer is doped to p-type so as to match the energy and form a resonance level, and the active layer is always present in the active layer.

[Effect]

In this invention, a quantum well or a superlattice doped with a p-type quantum well or a superlattice having a conduction band basis quantum level energy that resonates with a conduction band higher-order subband level energy of a semiconductor constituting an active layer is used. Since the electron injection layer is provided, electrons can be injected into the active layer efficiently and at high speed, and since holes are always present in the active layer, the light emission response can be improved.

(Example〕 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the structure of a superlattice semiconductor laser according to an embodiment of the present invention, in which 1 is an n-side electrode, 2 is an n-type ohmic layer semiconductor, 3 is an n-type cladding layer semiconductor,
4 is a superlattice for electron injection, 5 is a p-type active layer quantum well, 7 is a p-type rad layer semiconductor, 8 is a p-type ohmic layer semiconductor,
9 is an n-side electrode. Further, 6 is a p-type doped superlattice layer, which, together with 4, can also serve as a leading wave layer. In the electron injection cladding layer superlattice 4, the barrier layer 4a and the well layer 4b have a film thickness l.

By selecting the size of the band gap of 12 and the semiconductors constituting these layers, the lowest order (n=1) conduction band base quantum level acts as the thickness L2 of the active layer quantum well and its barrier layer. Among the conduction band quantum levels determined by the superlattice cladding layer, the second excited quantum level (n=2
) is set to match the energy.

Next, the operation will be explained.

Electrons injected from the n-side electrode with a forward bias pass through the n-type Ohmifuku layer 2 and the n-type cladding layer 3, and are injected from the electron injection superlattice 4 into the active layer 5, where they interact with holes in the active layer and emit light. They are recombined and amplified by a stimulated radiation process within the provided excitation resonator in a conventional manner to obtain laser oscillation. When electrons are injected from the superlattice layer 4 into the active layer 5, the electrons occupy the base quantum level within the superlattice layer due to intraband relaxation, so the base quantum level is located at the active layer quantum well. When the active M17 resonates with the second excited level (n=2), the electron energy transfer to the child well ground quantum level occurs through a quantum transition process, so it is fast and highly efficient. Implemented. On the other hand, holes are supplied by a p-type doped semiconductor, and holes are always present in the p-type doped active layer, so laser oscillation does not depend on the hole supply rate.

As described above, in this example, a superlattice structure is used for a part of the cladding layer for electron injection, and the conduction band higher subband quantum level energy of the semiconductor forming the p-type doped active layer is By matching the conduction band ground quantum level energy of the semiconductor forming the layer superlattice and forming a resonance level, an excellent superlattice semiconductor laser that can inject electrons into the active layer at high speed and with high efficiency has been realized. can.

In the above embodiment, the active layer 5 has one quantum well, and the conduction band bottoms of the well layers 4b and 6b in the superlattice layer are the same, that is, they are made of the same semiconductor. There may be a plurality of quantum well layers, and even if the semiconductor is different from the well layer in the superlattice layer, the same effect as in the above embodiment can be achieved as long as a resonant quantum level is created.

〔Effect of the invention〕

As described above, according to the present invention, in a superlattice semiconductor laser, a conduction band basis that resonates with the conduction band higher-order subband quantum level energy of a semiconductor constituting a p-type doped quantum well or a superlattice active layer. Since the structure includes an electron injection layer made of a quantum well or a superlattice layer having quantum level energy, it is possible to obtain a superlattice semiconductor laser with high speed and high injection efficiency.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a superlattice semiconductor laser according to an embodiment of the present invention and its potential diagram, and FIG. 2 is a diagram showing a conventional double heterojunction semiconductor laser and its potential diagram. 1 is an n-side electrode, 2 is an n-type ohmic layer semiconductor, 3 is an n-type cladding layer semiconductor, 4 is a superlattice layer for electron injection, 5 is a p-type active layer quantum well, 6 is a p-type superlattice, and 7 is a p-type semiconductor layer. A molded rad layer semiconductor, 8 a p-type ohmic layer semiconductor, and 9 a p-side electrode. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a superlattice semiconductor laser having a superlattice structure in the emission recombination region, a p-type doped quantum well or a superlattice active layer, and a quantum well that resonates with the higher-order subband level energy of the active layer semiconductor. 1. A superlattice semiconductor laser comprising an electron injection semiconductor layer made of a quantum well or a superlattice and having level energy.