JPH0485981A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To reduce generation of a spike and to reduce unnecessary power consumption based on a voltage drop by forming an intermediate layer exhibiting a composition change continued from the composition of one layer to the composition of other layer between layers formed with current narrowing parts having different energy bands between a contact layer and a clad layer. CONSTITUTION:A first intermediate layer 50 is formed between a P-type contact layer 12 and a ridge layer 14, and a second intermediate layer 52 is formed between the layer 14 and a P-type clad layer 16. The compositions of the layers 50, 52 are sequentially varied to adjacent layers. Thus, the composition is continuously varied from the layer 12 to the layer 16. Accordingly, since an energy spike generated in a hetero junction of a conventional structure is not generated and a voltage drop due to a hetero junction does not occur, a desired optical output can be obtained at a low voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser device having a current confinement portion, and particularly relates to improvement of a heterojunction interface of the current confinement portion.

[Prior Art] As a conventional semiconductor laser device having a current confinement section,
For example, there is a current narrowing structure as shown in figure jI5. In the figure, a driving current is supplied from the outside to the P electrode 10 and flows as indicated by the arrow in the figure.

Specifically, the current flows from the P-type contact layer 12 formed of P-type (conductivity type is P) GaAs to Ino, 5G
Passing through the edge layer 14 formed by ao, 5P, P-type I no, 5 (G a 1-XA l 5)
The P-shaped land layer 16 formed by C1,5P is reached. Furthermore, the current reaches the active layer 18 formed by I no, 5G a O-5P with no impurity implanted.

After that, the current is N type (conductivity type is N) In□, 5 (Ga
1-XA l x) 0.5N formed by P
Mold cladding layer 20. N-type electricity is transmitted through the N-type contact layer 22 formed of N-type GaAs! Leading to i24. In such a current flow, the active layer 18
Laser light is emitted. In this example, it is possible to emit laser light with a wavelength in the visible region.

[Problem M to be Solved by the Invention] By the way, the energy band from the P-type contact layer 12 to the P-type rad layer 16 in the electrode path of the semiconductor laser device as described above is as shown in FIG. 6, for example. As shown in the figure, energy spikes 26.28 appear due to energy band discontinuity of each layer at the heterojunction portions of each layer interface, that is, at the GaAs/InGaP and InGaP/InGaAIP interfaces. In addition, in the figure, Bc, Bv
respectively indicate the conductor's divalent electron band, and Ef indicates the Fermi level. FIG. 7 shows the relationship between such band discontinuities.

In the figure, the horizontal axis is the ratio value X of Ga and Al.

The horizontal axis shows band discontinuity values ΔEV and ΔEc for the conduction band and valence band of GaAs.

Spikes that occur at such a heterojunction interface26.2
8 is formed as a barrier (energy barrier) against holes. Therefore, when a driving voltage for the laser oscillation layer is applied to the device, a large voltage drop occurs at this portion. This means that when looking at the device as a whole, in order to obtain a predetermined optical output, a large voltage must be applied, which is the voltage required for light emission in the active layer 18 plus the voltage drop at the spikes 26 and 28. It turns out. Therefore, power consumption becomes larger than necessary.

Also, the power consumed by the spikes 26, 28 results in heat. As a result, the amount of heat generated by the device increases, resulting in deterioration of characteristics such as an increase in the oscillation threshold (threshold level).

Further, such heat causes the disadvantage that the laser life is shortened.

The present invention has been made in view of the above, and an object thereof is to provide a semiconductor laser device that can reduce unnecessary power consumption, and can effectively prevent characteristic deterioration and life shortening due to heat generation. That is.

[Means for Solving the Problems] The present invention provides a semiconductor laser device in which current confinement portions with different energy bands are formed between a contact layer and a cladding layer, in which a negative layer is provided between each of the layers. This layer is characterized by forming an intermediate layer that exhibits a continuous change in composition from one layer to the other layer's composition.

[Operations] According to the present invention, since the composition of the intermediate layer changes continuously, the energy bands between adjacent layers are well continuous, and the occurrence of spikes is reduced. Therefore, unnecessary power consumption due to voltage drops due to spikes is also reduced.

[Example] Hereinafter, an example of a semiconductor laser device according to the present invention will be described with reference to the accompanying drawings.

Note that the same reference numerals are used for components that are similar or equivalent to those of the conventional example described above.

FIG. 1 shows a main cross section of a semiconductor laser device according to this embodiment. In the figure, a first intermediate layer 5 is provided between the P-type contact layer 12 and the ridge layer 14 described above.
0 is formed, a ridge layer 14 and a P-type cladding layer 1
6, a 1!2 intermediate layer 52 is formed. That is, intermediate layers 50.degree. 52 are formed at the spikes 26 and 28, respectively.

Next, the manufacturing method of the above embodiment will be explained with reference to FIG. 2. First, as shown in FIG.
Each layer is formed in sequence.

To be more specific, the donor concentration as an impurity is approximately No. 1, for example.
On the N type GaAs substrate 22A of 018/cm3,
Crystal growth of each of the following layers is performed in order by the MOCVD method. In crystal growth by this MOCVD method, TMG, TMI, TMA, DMZ, SiH4, AsH3yPH3 are used as gases, and crystal growth is performed at a substrate temperature of 700°C.

(1) N-type buffer layer 22B made of N-type GaAs
(No. approx. 1018/cm3. Film thickness: 2 μm) (2) N-type I no, s (G ao, aA 10.7) 0.5
N-type cladding layer 20 made of P (No. approx. 5X1017/Q
m3. 1 μm in film thickness).

(3) Undoped In
Active layer 18 made of a, 5Gaa, 5P (film thickness approximately 067μ
m) (4) P type I no, 5 (G ao, 3A 10.7)
P-type cladding layer 16 made of 0.5P (acceptor concentration NA approx. 5 x 1017/cm3, film thickness 1 μm) (5) P-type 1no, 5 (Ga1-xAlx) Second intermediate layer 52 made of 0.5P (NA approx. 5X1017/cm3.x
The value of varies from 0.7 to O, 0.2 μm in film thickness) (6) Ridge layer 14 made of P-type I no, 5G a [1,5P (NA approximately 5×1o17/cm3, 0.2 μm in film thickness).
2μm) (7) First intermediate layer made of P-type InGaAsP 50°X
(GaAs) + (1-X) (InGaP), the value of X varies from O to 1 (NA about 5X101?/Cm3.
(film thickness: 0.2 μm) (8) P-type contact layer 12 made of P-type GaAs
(NA about 1018/cm3 film thickness about 0.1 μm) or more, in the first intermediate layer 50, X (GaAs) + (
1-8) (InGaP) is formed so that the value of X changes from O to 1.

That is, at the interface with the ridge layer 14, X is "o" and the composition is the same as that of the ridge layer 14. Then, the value of X gradually increases, and at the interface with the P-type contact layer 12,
X is "1" and the composition is the same as that of the P-type contact layer 12.

Moreover, the second intermediate #52 is also the same, I n port, 5 (G a 1-xA l x) 0
．． It is formed so that the value of X changes from 0.7 to O in 5P. That is, at the interface with the P-type cladding layer 16, X is ro, 7J and has the same composition as the P-type cladding N16. Then, the value of X gradually decreases, and at the interface with the ridge layer 14, X becomes "O" and is formed to have the same composition as the ridge layer 14.

Continuous changes in the composition of these intermediate layers 50, 52 are performed by changing the gas flow rate using the WfJ control program of the manufacturing equipment.

Next, after laminating each part as described above, 5i02. A mask 54 made of an insulator such as SiN4 is formed in an appropriate pattern. Thereafter, as shown in FIG. 2B, the ridge portion is etched.

Next, as shown in the same figure (C), a constriction layer 56 (No. 1
018/cm3. A film thickness of 1 μm) is formed around the ridge portion.

Furthermore, as shown in the same figure (D), an insulator mask 5
4 was removed and PyJ! P-type contact layer 12 made of GaAs (NAAlO218/cm3. 1 μm in film thickness)
) is formed. And each contact layer 12.22 has a P electrode 10 by A u / A u B e,
N electrodes 24 of A u /A u Ga are formed respectively.

Next, the operation of the above-described embodiment will be explained with reference to FIGS. 3 and 4. FIG. 3 shows the energy band structure from the P-type contact layer 12 to the P-type cladding layer 16, and FIG. 4 shows the current-voltage characteristics of this embodiment and the conventional example. .

As described above, in this embodiment, the intermediate layer 50.degree. Therefore, the composition changes continuously from the P-type contact layer 12 to the P-type land layer 16. Therefore, the energy spikes 26, 28 that occur at the interface in conventionally structured heterojunctions do not occur. Furthermore, in this embodiment, since a high concentration of P type is used, a valence band By that is substantially parallel to the Fermi level Ef is formed. That is, since there is no barrier against holes, which are the majority carriers of the P-type semiconductor, no voltage drop occurs at the heterojunction.

Therefore, when a Jot direction voltage is applied between the electrodes 10.24, there is no voltage drop due to the spikes 26.28, so a predetermined current flows at a lower voltage than before.
゛The desired light output can be obtained with low voltage. As shown in FIG. 4, in contrast to the conventional example of graph #1, graph #2
In this embodiment, current begins to flow at a voltage approximately 0°2V lower.

Note that the present invention is not limited to the above-mentioned embodiments; for example, the MBE method may be used instead of the MOC:VD method. Moreover, the composition change from the P-type contact layer 12 to the P-type cladding layer 16 can be carried out stepwise by forming a large number of counterfeit compositions with an energy gap difference of 25 m e V or less. , it is possible to obtain the same effects as in the above embodiment. In addition, even if the conductivity type of each part is reversed from that of the above embodiment, it is basically applicable.

[Effects of the Invention] As explained above, according to the semiconductor laser device of the present invention, an intermediate layer whose composition changes continuously in correspondence with the adjacent layer is formed.

Unnecessary losses due to energy spikes are prevented,
This has the effect that a predetermined optical output can be obtained with less power consumption, and characteristic deterioration and life shortening due to heat generation can be effectively prevented.

[Brief explanation of the drawing]

FIG. 1 is a structural cross-sectional view showing one embodiment of a semiconductor laser device according to the present invention, FIG. 2 is an explanatory diagram showing the manufacturing process of /H to P in the embodiment, and FIG.
An explanatory diagram showing the energy band from the type contact layer to the P-type cladding layer, Figure 3g4 shows the current -
A graph showing voltage characteristics, FIG. 5 is a cross-sectional view of the configuration of a conventional example, and FIGS. 6 and 7 are explanatory diagrams of the conventional example. 10.24... Electrode, 12.22... Contact layer, 14... Ring layer, 16, 20... Clad layer,
18... Active layer, 50.52... Intermediate layer, 54...
- Insulator mask, 56... constriction layer. Patent applicant: Japan Victor Co., Ltd. Akihito Patent attorney: Yasutoshi Kajiwara Figure 2 (D) Figure 3 GaAs Figure 3

Claims (1)

[Claims] In a semiconductor laser device in which a current confinement portion having a different energy band is formed between a contact layer and a cladding layer, a change in the composition of one layer from the composition of the other layer is provided between each of the layers. 1. A semiconductor laser device characterized by forming an intermediate layer exhibiting continuous compositional changes.