JPS6235592A - Quantum well semiconductor laser - Google Patents

Abstract

PURPOSE:To supply a quantum well semiconductor laser capable of generating a plurality of light beams of different wavelengths by one element by varying the thickness (width LZ) of a quantum well layer in response to the place. CONSTITUTION:An N-type AlGaAs enclosed layer 2 formed on an N-type GaAs substrate 1, a quantum well layer 3 enclosed on the layer 2 with partly different thicknesses LZ, a P-type AlGaAs enclosed layer 4, P-type side electrodes 5 (51-53) formed in a stripe shape, and N-type side electrodes 6 are formed. Such a quantum well laser element is integrated monolithically with lasers of 5 different wavelengths, and when a current is fed to the electrode 51, a laser light beam of wavelength lambda1 is emitted, and when a current is fed to the electrode 52, a laser light beam of lambda2 is emitted. Similarly, the laser light beams of different 5 wavelengths lambda3, lambda4, lambda5 can be separately emitted, or several or all the beams can be simultaneously emitted.

Description

[Detailed Description of the Invention] Summary of the Invention In an active region having a quantum well structure, the thickness and width of the quantum well layer vary depending on the location, and oscillation occurs at a plurality of different wavelengths. quantum well semiconductor laser.

[Technical Field] The present invention relates to a semiconductor laser, and more particularly to a quantum well semiconductor laser whose active region has a quantum well structure.

[Prior Art] Compared to conventional double heterostructure semiconductor lasers, quantum well semiconductor lasers have (1) good spectral monochromaticity;
(2) High selectivity of polarization plane.

It has advantages such as (3) good pulse response, (4) controllable oscillation wavelength, (5) low threshold operation, and (6) high temperature stability. has been widely studied. However, this type of quantum well laser that has been developed to date is a so-called single-wavelength laser, in which one element can only generate light of one wavelength; instead, it emits light of multiple wavelengths at the same time. There are no reports yet of the realization of a multi-wavelength laser that can do this.

Multi-wavelength lasers are extremely useful as light sources for wavelength-multiplexed optical communications, and their appearance is eagerly awaited.

Currently, as a substitute for multi-wavelength lasers, multiple lasers with different wavelengths are mounted close to each other and used.
There are problems such as the assembly is complicated, the shape is large, and the reliability is poor.

[Object of the Invention] An object of the present invention is to provide a quantum well semiconductor laser that can generate light of a plurality of different wavelengths with one element.

[Configuration and Effects of the Invention] The present invention is characterized in that, in a quantum well semiconductor laser in which the active region has a quantum well structure, the thickness and width L of the quantum well layer vary depending on the location. do.

The quantum well semiconductor laser according to the present invention utilizes the fact that the laser oscillation wavelength is determined by the width L of the quantum well layer, which is the active layer. It is known that the wavelength of a quantum well semiconductor laser is approximately proportional to L 2 .If L is made smaller, the wavelength becomes shorter, and conversely, if L is made larger, the wavelength becomes longer. Since quantum well active layers having partially different thicknesses are formed on the same wafer, it is possible to oscillate light of a plurality of different wavelengths simultaneously or by switching.

To form quantum well layers with partially different thicknesses on the same wafer, for example, during the molecular beam epitaxial growth of the quantum well layer, the growth substrate is partially covered with a metal mask, and the growth substrate is grown little by little at appropriate time intervals. By shifting the mask, it is possible to easily and reproducibly form a quantum well layer having a partially different thickness.

[Description of Embodiments] FIG. 1 shows an example of the structure of a quantum well semiconductor 1/-Z according to the present invention. This quantum well semiconductor laser includes an n-type GaAs substrate 1, an n-type AlGaAs confinement layer 2 formed on the substrate 1, and a quantum well layer 3 formed on the confinement layer z and having a partially different thickness L. , the p-type AlGaAs confinement layer 4 on the valve furnace layer 3, the p-type A
It consists of a P-side electrode 5 (51-55) formed in a stripe shape on the lGaAs confinement layer 4, and an N-side electrode 6 formed on the back surface of the substrate 1. In order to form the P-side electrode 5 in a stripe shape, an oxide film stripe method is used, in which the area other than the stripe portion is covered in advance with an oxide film such as 5i02, or a Brainer stripe method, etc. is used to diffuse Z 2 only in the stripe portion. is used. Further, a p-type GaAs electrode layer is usually formed on the p-type confinement layer 4 in order to lower the electrode resistance.

Next, a method for manufacturing a quantum well semiconductor laser having such a structure will be described with reference to FIGS. 3 and 4.

Figure 3 shows the molecular beam epitaxial growth mechanism when forming quantum well layers with partially different thicknesses.
An n-type AlGaAs confinement layer 2 is grown over the entire surface of an aAs substrate 1. This n-type AlGaAs confinement layer is
It has an Al mixed crystal ratio of 0.3, is doped with Si, has a carrier concentration of ~1018 cm', is n-type, and has a thickness of 2 to 34 cm.
It is m. In order to grow a quantum well layer 3 of different thickness and width depending on the location on this n-type AlGaAs confinement layer 2, the layer 2 of the substrate 1 is mask 11 at appropriate time intervals while applying the raw material molecular beam of Ga and As.
is shifted in the width direction of the striped window 12 and the GaAs
crystal growth.

This crystal growth process is shown in detail in Figure 4.
I+11 employment 1↓mu9-zuh-1small→[Nino h12 important text 2 and their interval fLf are set equal.

First, a quantum well with a thickness dl corresponding to the input oscillation wave 1 with the shortest wavelength is grown (FIG. 4a).

Next, the metal mask 11 is shifted to the right by 15 degrees, and a crystal is further grown on this layer (dl) to a thickness Ct + a2 corresponding to the second shortest wavelength (2).
Figure b).

Similarly, if crystal growth is performed while sequentially shifting the mask 11, ct, +d2 for every 2 and 15 mask shifts.
+d3. d, +d,, +d3+d4 ,d, +d2 +
GaAs quantum well layers having different thicknesses, a3+a4+d, are formed.

This process is an established mask vapor deposition method,
GaAg formed in this way has very good reproducibility.
A p-type rad layer 4 is formed on the entire surface of the quantum well layer 3, striped electrodes 5 and electrodes 6 are provided, and the substrate is divided at appropriate locations to complete a multiwavelength well semiconductor laser.

The quantum well laser device of this embodiment is one in which lasers of five different wavelengths are monolithically integrated, and the electrode 51
When a current is applied to the electrode 52, a laser beam with a wavelength of 1 is emitted, and the electrode 52
When a current is applied to the laser beam, a laser beam with a wavelength of 2 is emitted. Similarly, it is possible to emit laser beams of five different wavelengths (input 3, input 4, input 5) separately, or several or all at the same time. An example of each parameter is shown below.

AI Ga, xAs confinement layer 2.4 mixed crystal ratio x=0
．． 3. Oscillation wavelength (nm) AtO input 2 = 820 people, = 830 people, = 840 people, = 850 Parameters during quantum well layer growth (λ) d, = 68 d2 = 10 d3 = 10 d4 =12 As shown in FIG. 2, the thickness of the quantum well layer 3 may be changed continuously. In this case, the electrode 5 may be provided on the entire surface as shown in the figure, or may be provided in a striped form as shown in FIG.

This invention is based on a multi-quantum well structure (multiquantum well structure).
It can also be applied to lasers (mwell, MQW).

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a perspective view showing another embodiment of the invention, FIG. 3 is a diagram showing the molecular beam epitaxial growth method, and FIG. 4 is a partially thickened FIG. 3 is a process diagram showing in detail how quantum well layers of different sizes are grown. 1--GaAs substrate, 2-n-type AlGaAs confinement layer, 3...GaAs quantum well layer, 4...p-type AlG
aAs confinement layer. that's all

Claims (1)

[Claims] A quantum well semiconductor laser whose active region has a quantum well structure, wherein the thickness of the quantum well layer varies depending on the location.