JPS62166582A - Distributed feedback semiconductor laser device and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a sufficient oscillation in a distributed feedback semiconductor laser device by forming sequentially a first clad layer, an active layer and a second clad layer on a semiconductor substrate and a diffraction grating in the second layer to enhance a carrier enclosure efficiency. CONSTITUTION:An N-type Al0.3Ga0.7As layer 2 for forming a first clad layer, a GaAs layer 3 for forming an active layer, a P-type Al0.3Ga0.7As layer 4 for forming a second clad layer and a P-type Al0.15Ga0.85As layer 5 are sequentially epitaxially grown on an N-type GaAs substrate 1. Then, the layers 5, 4 are selectively etched until the layer 4 is partly exposed and becomes in thickness the same as that of the layer 5 to form a triangular uneven surface 6. Then, a P-type Al0.3Ga0.7As layer 7 for forming a third clad layer is epitaxially grown to cover the surface 6. Thus, a DFB layer having a secondary diffraction grating 8 with a P-type Al0.15Ga0.85As layer 5a is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a distributed feedback semiconductor laser in which feedback occurs through a periodic structure and laser oscillation is performed, and a method for manufacturing the same.

[Summary of the invention]

The first invention of the present application is such that sufficient oscillation can be obtained by arranging a diffraction grating in the cladding layer in the distributed feedback semiconductor laser as described above.

Further, a second invention of the present application provides a method for manufacturing a distributed feedback semiconductor laser as described above, in which a predetermined material layer is formed on the cladding layer, and the material layer and the cladding layer are selectively etched to form a periodic pattern. By forming irregularities, forming a cladding layer on the irregularities, and forming two cladding layers into one new cladding layer, manufacturing can be easily performed.

[Conventional technology]

distributed feedback type
k) Semiconductor laser (hereinafter referred to as DFB laser) is a single-
It is expected to be a laser that can achieve longitudinal mode oscillation.

Conventionally, in this DFB laser, a guide layer is further formed between the active layer and the cladding layer, a diffraction grating is formed in this guide layer, and light is distributed back by Bragg reflection by this diffraction grating. Ta.

[Problem that the invention seeks to solve]

However, in the conventional DFB laser as described above, the carrier confinement efficiency is low because the cladding layer is not in contact with the active layer, and sufficient oscillation cannot be performed.

[Means for solving problems]

The distributed feedback semiconductor laser according to the first invention of the present application includes a first cladding N2, which is sequentially arranged on a semiconductor substrate 1;
They each include an active layer 3, a second cladding layer 4.7, and a diffraction grating 8 disposed within the second cladding layer 4.7.

Further, the method for manufacturing a distributed feedback semiconductor laser according to the second invention of the present application includes the steps of sequentially forming a first cladding layer 2, an active layer 3, and a second cladding layer 4 on a semiconductor substrate 1;
By forming a predetermined material layer 5 on the second cladding layer 4 and selectively etching the material layer 5 and the second cladding layer 4, periodic irregularities 6 are formed on the surfaces thereof. and a step of forming a third cladding layer 7 on the unevenness 6, respectively.

[Effect]

In the distributed feedback semiconductor laser according to the first invention of the present application, first and second cladding layers 2 and 4.7 are provided on both sides of the active layer 3.
is arranged, so the carrier confinement efficiency is high.

Further, in the method for manufacturing a distributed feedback semiconductor laser according to the second invention of the present application, the second cladding layer 4 and the third cladding layer 7
becomes a new second cladding layer 4.7, a predetermined material layer 5 selectively etched to form periodic irregularities 6 is disposed within the new second cladding layer 4.7, This material layer 5 becomes a diffraction grating 8.

〔Example〕

Below, D of AlGaAs/GaAs heterostructure
An embodiment of the present invention applied to an FB laser will be described with reference to FIG.

In this example, as shown in FIG. 1A, first, n-GaA
n-8 10. constituting the first cladding layer on the s-substrate 1;
3 Gao, t As layer 2, GaAs constituting the active layer
Layer 3, p-Δ1°, 1Ga constituting the second cladding layer
The 0.7As layer 4 and the pAIo, +5Gao, and 8BAs layers 5 are epitaxially grown in sequence by MBE or MOCVD. Furthermore, p-8io, +5Gao
, 85The thickness of the AS layer 5 is approximately half the height of the unevenness 6, which will be described later.

Next, using the holographic ink exposure method, which is known as a normal method for producing second-order diffraction gratings as shown in Figure 3,
pAlo,i Gao,7 As layer 4 is partially exposed and further p-8Io, +5Gao,5s pAlo,+5Gao,e is removed until the As layer 4 reaches a depth approximately equal to the thickness of p-8Io, +5Gao,5sAs layer 5.
sAs layer 5 and p-AI. , 3Ga, , As layer 4 is selectively etched.

Then, as shown in Figure 1B, 1o to p-, + 5G
ao, asAs layer 5 and p-8I. , 3 Ga(,,)
Triangular wave-like unevenness 6 is formed with the center line at the interface with the As layer 4.

Note that the second-order diffraction grating with the shape shown in Fig. 3 will not work if the exposure intensity distribution is to a certain extent due to the anisotropy (crystal plane dependence) of the semiconductor substrate and the etching solution. , can be produced in a self-consistent and reproducible manner.

Next, the first C
As shown in the figure, p-AI constitutes the third cladding layer.

, 3 Ga, , As layer 7 is epitaxially grown to cover the unevenness 6 .

Then p-810. :l Gao, S layer 4 and 7 to 7
becomes a new second cladding layer, and p Alo, +5Gao, which has a triangular cross section left during the etching described above,
The as^S layer 5a is arranged in the new second cladding layer 4.7.

However, the configuration shown in FIG. 1C has substantially the same periodic structure as the second-order diffraction grating shown in FIG.
This means that a DFB laser having a second-order diffraction grating 8 made of +5 Gao and esAs layers 5a has been manufactured.

According to this embodiment as described above, the DFB has the second-order diffraction grating 8 having the periodic structure substantially the same as the second-order diffraction grating shown in FIG. 4, which has the maximum first-order Fourier component and strong coupling with light. The laser is manufactured by the same method as the second-order diffraction grating shown in Fig. 3, which has a first-order Fourier component of O and has weak coupling with light, but can be manufactured with good shape uniformity and reproducibility. be able to. Therefore, the DFB laser according to this embodiment can obtain sufficient oscillation even though the shape uniformity and reproducibility are good.

Moreover, the height of the triangular wave-like unevenness 6 is p-AI. , I5G
The thickness of the ao and asAs layer 5 can be controlled by the thickness of the layer 5, but in the above embodiment, the MB2 method or M
Since the OCVD method is used, the height of the unevenness of the second-order diffraction grating 8 can be easily controlled. Therefore, also due to this fact, the DFB laser according to the above embodiment has good shape uniformity and reproducibility.

In addition, in the above-mentioned embodiment, p-
Although the Alo, r5Gao, and asAs layers 5 were formed, any material that can form the triangular wave-like unevenness 6 as shown in FIG. 1B by etching may be used.
I. 15Ga. , 5sAs layer 5 may be replaced by another material layer, for example, an AlGaAs layer having a different Al composition.

Furthermore, in the above-described embodiments, the invention of the present application is applied to a DFB laser having a second-order diffraction grating 8, but for example, a DFB laser having a third-order diffraction grating or a higher-order diffraction grating as shown in FIG. The invention of the present application can also be applied to. In addition, D other than AlGaAs/GaAs heterostructure
It is also possible to apply the invention of the present application to an FB laser.

(Effects of the Invention) In the distributed feedback semiconductor laser according to the first invention of the present application, sufficient oscillation can be obtained because the carrier confinement efficiency is high.

Further, in the method for manufacturing a distributed feedback semiconductor laser according to the second invention of the present application, by forming the third cladding layer, a diffraction grating is automatically arranged in the new second cladding layer, and selective etching is also performed. Since the unevenness can be formed by a conventional method, the distributed feedback semiconductor laser according to the first invention of the present application can be easily manufactured.

[Brief explanation of drawings]

1A to 1C are DFs according to an embodiment of the invention of the present application.
A cross-sectional view showing the manufacturing method of the B laser in the order of steps, Figure 2 is 3.
FIG. 3 is a cross-sectional view of a second-order diffraction grating in which the first-order Fourier component is 0, and FIG. 4 is a cross-sectional view of the second-order diffraction grating in which the first-order Fourier component is maximum. In addition, in the reference numerals used in the drawings, 1----------- n -GaAs substrate 2----
----------n Alo, xGao, 8S
Layer 3-----------Ga As layer 4.1'-"'-'pAlo, :+Gao, 7As layer 5
−−−−−−−−−−−−− 1o to p-, + 5
Gao, a5As layer 6...---------...
−Triangular wave-like unevenness 8−−−−−・−・・−−−−−−−−
This is a second-order diffraction grating.

Claims (1)

[Claims] 1. A first cladding layer, an active layer, and a second cladding layer that are sequentially arranged on a semiconductor substrate, and a diffraction grating that is arranged in the second cladding layer. Distributed feedback semiconductor laser equipped with each. 2. A first cladding layer, an active layer and a second cladding layer on a semiconductor substrate.
forming a predetermined material layer on the second cladding layer; and selectively etching the material layer and the second cladding layer. A method for manufacturing a distributed feedback semiconductor laser, comprising the steps of: forming periodic irregularities on a surface; and forming a third cladding layer on the irregularities.