JPS62120093A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain a coating film having a thickness of about 200Angstrom and still having a high density and to enable the end faces of a semiconductor laser to be coated with a high yield without deteriorating the optical reflectivity at the end faces, by forming the coating film of Ta2O5. CONSTITUTION:An N-type GaAs substrate 1 having a (100) face on one surface is provided with a 6mum wide and 1.5mum deep groove. A first clad layer 2, an active layer 3, a second clad layer 4 and a cap layer 5 are deposited on the surface of the substrate 1 in that order. Then, end faces 1a and 1b of a resonator thus constructed is coated with a film of Ta2O5 6 having a thickness of 200Angstrom . The data curve with O mark chain represents the relation between the thicknesses of the Ta2O5 film 6 and the dielectric loss tangent indicating the densities thereof. Another data curve with (x) mark chain represents the same relation of an Al2O3 film formed by means of the high-frequency spattering. The coating film 6 of Ta2O5 can be formed in such a short period as two or three minutes, and therefore little irregularity is caused in the thickness of the film. Consequently, the variation in reflectivity on the end faces can be also limited to 1% or less.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to a semiconductor radar.

(b) Conventional technology Currently, as a coating film on the end face of a semiconductor radar, the refractive index of the coating film is 1i (normal deviation) and the thickness? Az with
ZOS (alumina) film, 51SNJ silicon nitride) film, etc. are used.

eC Problems to be Solved by the Invention In general, when At201 (nA=1β5) is used as the end face coating material of a semiconductor laser whose oscillation wavelength is about 5ooo It is necessary to do so.

However, although such coating films can usually be produced using high-frequency sputtering rigs, it is extremely difficult to maintain sputtering conditions such as substrate temperature and high-frequency electric field constant for long periods of time with currently used high-frequency sputtering equipment. However, slight fluctuations in the sputtering conditions cause the film formation rate to fluctuate by about 20%.

For example, when growing At20m with a thickness of 2420A as an end face coating film of a semiconductor radar.

Even if the sputtering conditions were set so that the film formation rate was 100 A/min and high frequency sputtering was performed for 24 minutes, the thickness of the grown film would deviate from the desired value by about 484 A.

When such a film thickness error occurs, the light reflectance at the semiconductor laser end face decreases by about 7 inches, resulting in an increase in threshold current and a reduction in the life of the semiconductor laser.

■ Therefore, focusing on the fact that the relationship between the light reflectance at the edge of the semiconductor radar and the thickness of the coating film forms a cosine curve as shown in Figure 5, it was decided to set the end face coating film to about 200A. is considered.

In this way, if the end face coating film is 20OA thick,
The growth time of such a film is about 1° compared to when forming a film with a thickness of 2420A, so there was no thickness error due to variations in sputtering conditions, and there was no decrease in the light reflectance of the end face. It is about 2%, and no substantial increase in threshold current is observed.

However, the thickness of films such as At2os and S1-N4 is 1
If it is less than 000A, the density is poor, and there is a problem in that oxygen and the like enter the end face of the semiconductor radar through the film and deteriorate the end face.

(b) Tth means to solve the problem The present invention has been made in view of these problems.

Its structural features are the f@-plane co-coating film and Ta20
3 (pentaacid intal)? There are nine uses.

(e) Effect The film made of the above-mentioned 'razo5 is highly dense even at a film thickness of about 200 layers.

(f) Example Figures 1 and 2 show an example of the present invention. Figure 1 is a sectional view taken along line I-1' of the second factor, and Figure 2 is a sectional view taken along line 1-1' of Figure 1. FIG.

In the figure, (1) is an n-type Ga whose main surface is the (100) plane.
It is an As substrate, and the carrier concentration of the substrate is 1 to 2X 1
0"V4. Also, a groove extending in the direction perpendicular to the paper plane in FIG. 1 is formed on one main surface of the substrate, and the width of the groove is 6.
μm, and the depth is 1.5 μm. (21 is the above board (1
) is a first cladding layer laminated on one main surface of
Type GaO, consisting of 5 mt 0.5 A B.

The layer thickness is 1 to 2 μm at the top of the groove, and 0.1 to 0.3 μm at the other portions (hereinafter simply referred to as flat portions).

[3] is a t active layer laminated on the first cladding layer (21), and the active layer has a carrier concentration of 10111 to 10
/7 non-doped Ga0.85 At O,15A
8, and its layer thickness is α1 μm. 14] is a second cladding layer laminated on the active layer (3).

The layer thickness is 1.5 μm at the top of the groove so that the surface is flat.

1.2μm binding on flat part 7'? :, +51 is the second cladding layer (n9 cap layers stacked on top of 41),
The cap layer has a carrier concentration of 5×101a to 5×
The thickness of the 7O layer is 0.5-1.5 μm. (6) is made of PlJGaAs of 10”79.
) (It is a coating film formed on the lb layer, and the coating film is made of Ta205, and its film thickness is 200 mm.
It's a person.

Such a coating film has a mixing ratio of argon and oxygen of 9:
10 Ta to the target in the atmosphere! It can be formed by performing minute wave sputtering for 2 to 3 minutes at a substrate temperature of 140° C. to 150° C. and an input power of 150 W.

In Figure 3, the data marked with ○ are formed by high frequency sputtering and the frame is 7tTa! The relationship between the thickness of the FT-At20B film and the dielectric loss tangent indicating density 2 is shown, and the data curve marked with tx is formed by high-frequency sputtering. show.

The dielectric loss tangent becomes smaller as the density of the film increases.

Therefore, it is clear from the 3rd ward (20 consisting of Ta205
A film with a thickness of 0A has the same density as a film made of At201 and having a thickness of 1000 Å or more.

The light reflectance at the end face of a semiconductor laser having a 200A thick coating film (1) made of Ls Ta206 is A.
T! The light reflectance of the end face τ of a semiconductor radar having a coating film of 2420A thick made of 08
%, and has almost no relation to the increase in threshold current.

Figure 4 shows the results of measuring the lifespan of the wooden embodiment device (marked with ○ in the figure) and the lifespan of a conventional device that forms a coating film with a thickness of 242OAtgos (marked with Δ in the figure). This study investigated changes in the operating current of a semiconductor radar when continuous rooting was performed at 5 mW in an atmosphere at 60°C.

As is clear from FIG. 4, the wood-embodiment device also has the same life characteristics as the conventional device.

Further, since the coating film f81 of the thick embodiment can be formed in a short time of 2 to 3 minutes, there is little variation in film thickness, and as a result, variation in reflectance at the end face can be suppressed to within 1 inch.

(g) Effect of the invention As in the present invention, the coating film on the end face of the semiconductor radar is coated with T.
a! If it is made of Oe, it is possible to obtain a dense film with a thickness of about 200A.

End face coating can be performed at a high yield without reducing the light reflectance at the end face of the semiconductor radar.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention, FIG. 1 is a sectional view taken along line 1-1' in FIG. 2, FIG. 2 is a sectional view taken along line I-I of the first factor, and FIG. is a characteristic diagram showing the relationship between film thickness and dielectric voltage contact,
FIG. 4 is a characteristic diagram showing the life characteristics, and FIG. 5 is a schematic diagram showing the general relationship between the coating film thickness on the semiconductor radar end face and the light reflectance at such end face. +61-...Coating film.

Claims (1)

[Claims] (1) A semiconductor laser characterized in that Ta_2O_5 (tantalum pentoxide) is used as an end face coating film.