JPS61182295A - Semiconductor layer device - Google Patents

Abstract

PURPOSE:To enable an oscillation at a single longitudinal mode on nonstationary operation by applying a reverse bias to a junction section between a first clad layer and a block layer constituting a semiconductor laser device having double hetero-structure and changing a gain or an absorption coefficient at a period in the same extent as an optical wavelength to the direction of propagation of beams. CONSTITUTION:An N-type InP buffer layer 3, an InxGa1-xAsyP1-y (0.47<x<1, 0<y<1) active layer 4, a composition thereof is determined so that an oscillation wavelength extends over 1.1-1.6mum, a P-type InP first clad layer 5, and an N-type InP block layer 6 are laminated and grown in an epitaxial manner on an N-type InP substrate 2. A lattice pattern having a period of 1700-2500Angstrom is shaped on the surface of the layer 6, and a P-type InP second clad layer 7 and an N-type InP cap layer 8 are grown on the lattice pattern. A striped P-type channel 11 intruding to the layer 7 is formed to the layer 8 and used as a current path, a junction section between the layers 5 and 6 is brought to a reverse bias, and the gain of the layer 4 is lowered by a lattice, thus stabilizing an oscillation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a distributed feedback semiconductor laser device that oscillates in a single longitudinal mode.

(Prior Art) Conventionally, a nine-distributed feedback semiconductor laser has been used to realize single-longitudinal mode oscillation. but.

In this type of distributed feedback semiconductor laser, there are two longitudinal modes with essentially the same gain, and during steady operation where a constant current is always flowing.

Due to the inherent asymmetry of the resonator, it is thought that it oscillates in only one longitudinal mode.

That is, in a conventional distributed feedback semiconductor laser.

One cleavage plane is etched diagonally so that the cleavage planes at both ends do not form a Fapley-Perot resonator.
As a result, the asymmetry of the resonator is intentionally increased, and stable single-longitudinal mode oscillation is realized.

(Problems to be Solved by the Invention) However, 2. For example, when this type of distributed feedback semiconductor laser is used as a light source for optical communication, the amount of excitation current is modulated at high speed, so even if the resonator is configured asymmetrically, However, it does not necessarily oscillate in a single mode; in fact, broadening of the oscillation spectrum and discontinuous changes in the oscillation mode have been observed.

In view of this, an object of the present invention is to provide a distributed feedback semiconductor laser capable of oscillating in a single longitudinal mode not only during steady operation but also during unsteady operation.

(Means for Solving the Problems) The present invention provides a double heterostructure semiconductor laser device in which a first cladding layer of a certain conductivity type is formed on an active layer, and a first cladding layer of a certain conductivity type is formed on the first cladding layer. A semiconductor layer (block layer) having a conductivity type opposite to that of the first cladding layer is formed at regular intervals in a direction perpendicular to the light propagation direction, and a second cladding layer having the same conductivity type as the first cladding layer is formed on this semiconductor layer. This is a semiconductor laser device in which a periodic current blocking structure is formed by the first cladding layer and the semiconductor layer (block layer) which are reverse biased.

(Function) By applying a reverse bias to the junction between the first cladding layer and the semiconductor layer (block layer), the gain or absorption coefficient changes in the light propagation direction with a period comparable to the wavelength of the light. Single longitudinal mode oscillation occurs even during steady operation.

(Example) Hereinafter, two embodiments of the present invention will be described with reference to the drawings.

The drawing is a perspective view of a distributed feedback semiconductor laser according to the present invention. In the distributed feedback semiconductor laser of this example, I nx
Ga+-xAs, P+-, (0,47<x<1°0<
A p-type 1nP first cladding layer 5 is formed on the active layer 4 consisting of y<1), a lattice-shaped n-type InP block layer 6 is formed on this p-type 1nP first cladding layer 5, and A p-type 1nP second cladding layer 7 is formed on the 1nP block layer 6, and a reverse bias is applied to the junction between the p-type InP first cladding layer 5 and the n-type 1nP block layer 6.

Note that the p-type 1nP first cladding layer 5. n-type 1np block layer6. Although the three layers of the p-type 1nP second cladding layer 7 do not need to be made of the same material, the p-type 1nP first cladding layer 5
and p-type 1nP second cladding layer 7.

It is necessary that the energy gap is larger than that of the active layer 4 and that the conductivity types are the same.
nP first cladding layer5. p-type InP second cladding layer 7
It is necessary that the conductivity type is opposite to that of .

Next, the manufacturing procedure of the distributed feedback semiconductor laser having the above configuration will be described.

■ First, an n-type 1nP buffer layer 3 is grown on an n-type InP substrate 2 by a liquid phase growth method, and then a composition that provides an appropriate oscillation wavelength of about 1 μm to 1.6 μm is grown. The active layer 4 consisting of the following ratio is grown.

■ A p-type 1nP first cladding layer 5 of approximately 0.08 μm is grown on this active layer 4, and an n-type TnP blocking layer 6 is grown on the active layer 4.
is grown to a thickness of about 0.1 μm.・Then, a photoresist mask (not shown) is applied, and an interference fringe pattern of 1,700 to 2,500 people is exposed for 2 cycles using, for example, a 2-beam interference exposure device, and the period is about the same as the wavelength of the light. Make a mask with a grid pattern. Using this mask, etchant (saturated bromine water: H3P0a: HtO
= 2:1:15 composition ratio) makes n-type 1nP
The block layer 6 is removed by etching in a grid pattern.

■ Next, a p-type InP second layer is placed on the n-type 1nP block layer 6.
A cladding layer 7 and an n-type 1nP cap layer 8 are grown, and then a +SiNx film 9 is deposited to a thickness of approximately 2000 nm by, for example, plasma CVD, and a photoresist mask (not shown) is used to align the film in the direction of light propagation. Etching is performed in stripes along the wafer using an etching solution (having a composition of HF:NH4F=1:40). Using this SiNx film 9 as a mask, an easily diffusable impurity element such as Zn is diffused to form a P-type channel 11, which serves as a current path. Finally, electrode 1 and electrode 10 are formed.

Therefore, in the distributed feedback semiconductor laser having the above configuration, the electrode 10 side is set at a positive potential with respect to the electrode 1 side,
p-type 1nP first cladding layer5. When the junction with the n-type 1nP block layer 6 is reverse biased, a lattice-like current blocking structure is formed by this junction.
The active layer 4 directly under the nP block layer 6 has a lower gain than the other portions. By lowering this gain, it is possible to obtain single-longitudinal mode oscillation similar to the conventional distributed feedback semiconductor laser in which the refractive index is changed along the light propagation direction at a period comparable to the light wavelength. .

Moreover, in the case of this example, stable longitudinal mode oscillation was confirmed not only during steady operation but also during unsteady operation.

5 The distributed feedback semiconductor laser according to the present invention has the above-mentioned I n P / I n Ga As P /
Although the application to an r n P double hetero type semiconductor laser has been shown, other semiconductor lasers such as GaAAA
s / Ga As / In Ga As
It can also be applied to a P double hetero type semiconductor laser.

(Effects of the Invention) As described above, 1. According to the present invention, a distributed feedback semiconductor laser that oscillates in a single longitudinal mode oscillation not only during steady operation but also during unsteady operation has been confirmed. for example,
It also enables extremely durable and stable oscillation as a light source for optical communications.

[Brief explanation of drawings]

The drawing is a perspective view showing an embodiment of a semiconductor laser device according to the present invention. 4... Active layer 5... P-type 1nP first cladding layer 6... N-type 1nP block layer 7... P-type 1nP second cladding layer and one other person

Claims (1)

[Claims] 1) In a double heterostructure semiconductor laser device, a first cladding layer of a certain conductivity type is formed on the active layer, and a semiconductor layer of a conductivity type opposite to the first cladding layer is formed on the first cladding layer. A second cladding layer is formed at regular intervals in a direction perpendicular to the propagation direction of the semiconductor layer, and has the same conductivity type as the first cladding layer, and the first cladding layer and the semiconductor layer are reversely biased. A semiconductor laser device characterized in that a periodic current blocking structure is formed by.