JPS5873175A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To facilitate manufacture, and to improve the temperature characteristics, etc., of a semiconductor laser by a method wherein epitaxial growth layers containing an active layer formed in a groove are formed in the manner not to extend over the dielectric film adhered on the main surface of a semiconductor substrate. CONSTITUTION:A dielectric layer 12 of Si3N4 is formed according to the CVD method on a semionductor substrate 1, and patterning is performed according to the photoetching method. After a groove is formed according to the chemical etching method, etc., a first semiconductor layer 6 consisting of N type InP, a second semiconductor layer 7 consisting of InGaAsP, a third semiconductor layer 8 consisting of P type InP and a fourth semiconductor layer 9 consisting of P type InGaAsP are formed by crystal growth according to the liquid phase epitaxial growth method. According to the liquid phase epitaxial growth method, the crystal is not grown on the dielectric film 12 being amorphous like Si3N4, and is grown only in the groove, and the manufacturing yield of the semiconductor laser is improved, and after then, a first electrode 10 and a second electrode 11 are adhered on both the faces, and the temperature characteristics, etc., are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a new semiconductor laser that has a single oscillation transverse mode, can obtain high-quality light with a low threshold value, and is easy to manufacture.

Figure 1 shows B C, (Buried Crescent
FIG. 1 is a plan view showing an example of a conventional semiconductor laser called a buried crescent laser.

This semiconductor laser is deposited on an n-1nP substrate crystal (1).
−1nP(2)* n −1nGaAsP (31+
After sequentially growing p-InP (4) and n-InP (f+), a mask was formed by photolithography, a groove was formed by chemical etching, and the mask material was removed.
(6n, InGaAsP (7), p-1n
P (8) and p -1nGaAsP (9) were sequentially grown, a positive electrode ring and a negative electrode Qv were formed using a vacuum evaporation method, and then the grooves were bent perpendicular to the grooves. In this BC type laser, the second grown InGaA
Electrons from n -1nP (6) to sP (7), p -
Holes are injected from 1nP(8) and recombine radiatively.

This InGaAsP (7) is called an active layer because it is electro-optically active. Also, InGaAs
The forbidden band width of P (7) is n-1nP(6) or p -1
It is narrower than nP (8) and has a larger refractive index.

If the width is ~8 μm, the shape will be like a waxing trident as shown in FIG. 1, so light will be confined within a narrow range of 1 μmN degrees in the center for the same width.

Therefore, the oscillation transverse mode allowed in the active layer (7) is limited to the fundamental mode, resulting in single mode oscillation.

However, in this BC type laser, the effective current flowing to the active layer (7) in the groove is not n -1n
P f5), p -1nP (4), n -1nG
There is also a reactive current flowing through the aAsP (3) section. This invalid current is p −InP (4) and n −1nP
It is devised so that it can be reduced by the reverse bias in (5). However, the area of the region where this reactive current flows is 200 times larger than the effective groove area, so it can be ignored.The reactive current increases rapidly as the temperature rises, and is the dominant factor that deteriorates the temperature characteristics of the laser. It becomes. In addition, manufacturing this BC type laser is characterized by an elaborate and difficult process in which a part of the crystal is grown, a groove is formed, and the crystal is grown again. All of them have poor flatness and are not suitable for fine patterning, and it is difficult to make the width uniform.

The present invention has been made in view of these points, and takes advantage of the fact that in the liquid phase epitaxial method, it does not grow on an amorphous dielectric # film, and is formed in the groove of the C1 substrate. On the n -1nP substrate crystal (1) in Figure 8a,
An i3N4 film (2) is formed (FIG. 8b) and patterned by zeta photolithography (FIG. 8C).

Next, a vortex is formed using a reactive ion etching method or a normal chemical etching method (Fig. 8d), and a liquid phase epitaxial method is used to form an n-1nP (6), InGa
AsP (7) e p-InP (8) and p-In
GaAsP (9) is grown as a crystal (Fig. 8e). At this time, in the liquid phase epitaxial method, growth does not occur on an amorphous dielectric film such as Si3N4, so it grows only within the groove. Thereafter, metal is deposited on both surfaces using a vacuum evaporation method to form a piezo electrode QQ and a negative electrode (b) (FIG. 8f).

This embodiment device is similar to the conventional device shown in FIG.
In the case where AsP (7) acts as an active layer and the positive polarity αQ is insulated by the dielectric thin film (2) other than the groove, no current flows anywhere other than the groove, completely eliminating reactive current. The temperature dependence of the oscillation threshold is also good, and 70°
Continuous oscillation is possible even in a high temperature atmosphere of C or higher. The mode characteristics of the oscillated light are as good as those described in the conventional example.

In addition, each layer is formed using a liquid phase epitaxial method.
This is due to the following reason. Gas-phase epitaxia has irregularities corresponding to the grooves, making it difficult to form electrodes. Furthermore, when this grown surface is not soldered to the heat sink, the groove portion comes into contact with the heat sink by the thickness of the crystalline layer on the HTA thin film, resulting in poor heat dissipation.

If it is replaced, the bonding time will increase, and many problems will occur, such as deterioration of characteristics and shortening of life. In this respect, in the liquid phase epitaxial method, Si3N, which is an amorphous cystoelectric thin film, is
There was no growth on the 4th gland (2), and InGaAsP
On top of (7), when the composition is prohibited from the above InGaAsP (7), p -1nGaAsP (2)
The composition is such that the emission wavelength is 1.1 μm. in this case,
The light generated in the active layer (7) is p -1nGaAsP
The forbidden band width of Qa is p -InP (8) or n -1nP
(6) Because it is narrower than p-InP (8) and n
-InP (greater than 61, p -1nGaAsP
The waves also spread to Asia and are guided. By spreading the light and guiding it in this manner, it is possible to achieve high output and to narrow the spread of the emitted laser beam. p-1nGaAsPO having such an effect will be referred to as an optical waveguide layer. The electrical conductivity types, p-type and n-type, are not directly related to the waveguide effect of light. Therefore, this optical waveguide layer (to) may be placed under the active HIJ (7) to make it n-type.

Although the above embodiments were explained using an n-type substrate crystal,
All conductivity types may be interchanged. In addition, InP is used for the substrate.
Although an example using a single crystal has been shown, the same can be said of using GaAs. For example, in Figure 2, (1) is replaced by n-GaA
s, (6) as n Al0-4 Gao, s As
I (7) to p-Alx al-xAs (x≦0.8
), '(8) p AIo, 4Ga6,6 As
*(9) may be p-GaAs. In addition, in Fig. 4, (1) is n -GaAs, (6n is n -
AIo, 4 Gaes As * (7) as p -Al
xGa+-xAs, G:I p-A1yGa+-y
As(x<y<.

0.4 > , (8) as p-AIo, , Ga, ,
6As, (9) may be combined with p-GaAs.

Of course, the same applies to those in which these conduction types are interchanged.

Among these, (1) is p -GaAs [ , Seita crystal, (6) is p -AIo, 4 Gao, a
As, (7) as p-AlxGarxAs, Q
a to n-AlyGa+-yAs (x<y<0.4)
.

(8) as n -AIo, 4 Gao, g As, (9
) is made of n-GaAS, which is excellent in that the resistance can be ground by widening the p-type crystal, which is difficult to obtain a low-resistance electrode.

Alternatively, the substrate crystal may be made of GaAs, and each layer grown in the groove may be made of another 1-V group compound semiconductor such as AlInGaP.

Furthermore, as mentioned earlier, the dielectric thin film formed on the substrate crystal has a high degree of flatness and is relatively easy to finely pattern and etch, as shown in FIG.
It is also possible to form a plurality of grooves with high precision. In this way, it becomes easy to connect the semiconductor lasers A and B with the semiconductor laser C to manufacture a phase-synchronized semiconductor laser.

As described above, the present invention provides excellent semiconductor lasers that can be produced using a relatively simple manufacturing method, in a short period of time, and with a high yield, as well as having a low threshold value and excellent temperature characteristics. have an effect.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing an example of a conventional semiconductor laser;
Figure 98 is a cross-sectional view showing one embodiment of the present invention, Figure 98 is a To1 side view of the process showing an example of its manufacturing method, Figure 4 is a cross-sectional view showing another embodiment of the present invention, Figure 6 FIG. 2 is a perspective view showing an example of application of the present invention. In the figure, (1) is the semiconductor substrate, (6) is the first semiconductor layer, (7) is the second semiconductor layer, (8) is the eighth semiconductor layer, QIJ is the first wt pole, and 0υ is the second electrode, (6)
is the transparent layer, and (to) is the fourth half-body layer. In addition, the same numbers in the figures indicate the same or corresponding parts.
Bus. Applicant: Director of the Agency of Industrial Science and Technology Ishizaka h -No. 1- Fig. 2 Fig. 3

Claims (5)

[Claims] (1) A semiconductor substrate of type 14 with a groove provided on one main surface; an epitaxial growth layer including an active layer formed in the groove so as not to extend over the dielectric film; a first t-pole continuously deposited on the epitaxial growth layer and the dielectric film; and the semiconductor. A semiconductor laser including a second electrode deposited on the other main surface of the substrate. (2) The epitaxial growth layer includes a first semiconductor layer of the first conductivity type that is sequentially layered from the bottom of the trench, and a second semiconductor that has a narrower forbidden band width than this first semiconductor layer and that provides active #I. 2. The semiconductor laser according to claim 1, comprising at least an eighth semiconductor layer of the second conductivity type having a wider forbidden band width than the second semiconductor layer. (3) A second turtle-shaped fourth semiconductor J whose forbidden band width is wider than the second semiconductor layer and narrower than the eighth semiconductor layer, between the second semiconductor layer and the eighth semiconductor layer. - A semiconductor laser according to claim 2, comprising: -. (4) Between the first semiconductor layer and the second semiconductor layer, a fifth semiconductor layer of the first conductivity type whose forbidden band width is narrower than that of the first semiconductor layer and wider than that of the second semiconductor layer. A semiconductor laser according to claim 2, which is made by itself. (5) The semiconductor laser according to claim 1, wherein the epitaxial growth layer is formed by a liquid phase epitaxial growth method.