JP2709108B2 - Mask semiconductor laser - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser suitable for a point light source, and more particularly, to a mask semiconductor laser applicable to an optical memory pickup and other devices using a point light source.

[Conventional technology]

The inventors have proposed a mask semiconductor laser as a device that can realize a substantially ideal point light source.

The mask semiconductor laser has a mask layer that blocks light emitted from the semiconductor laser, and a part of the layer is provided with emission light of the emitted light. As a method of forming the emitted light, for example, it is possible to irradiate a part of the mask layer with the radiation light of the semiconductor laser itself to be used, to remove the part to form a hole, and to use another known method. Can also. The basic technology of the mask semiconductor laser is disclosed in Japanese Patent Application Laid-Open No. 63-34991.

Also, as a mask material to prevent damage to the semiconductor laser when making a circular or slot-shaped opening in the light emitting surface to improve the characteristics of the semiconductor laser
There is a technique using a Bi-based material (US Pat. No. 3,866,238).

[Problems to be solved by the invention]

Since the mask semiconductor is used, for example, as a light source for high-density recording and reproduction, it is desirable that the exit hole be a fine pinhole close to a so-called sharp circular shape with a clean cut end.

However, the shape of this pinhole is greatly affected by the manufacturing conditions of the film of the mask layer, and it is very difficult to form a pinhole that is close to a circle and has little residue.

In order to prevent the pinhole accuracy from changing over time, a high melting point material must be selected as a material for the mask layer.However, in this case, the pinhole cannot be easily opened with the power of the semiconductor laser, Means (conditions) for achieving one object achieves another object, for example, if the film layer to be easily opened is made thin, there is no problem with the sharpness of the pinhole, but the shape becomes oval. This is because there is a relationship that is an obstacle.

Therefore, an object of the present invention is to provide a condition that a pinhole can be formed relatively easily with the radiation light of the semiconductor laser itself without causing a temporal change of the pinhole accuracy, and that the processing accuracy is also good. It is to provide a mask semiconductor.

[Means for solving the problem]

The present invention provides IIIb-IV
The mask layer is made of a material obtained by adding a Group Ib or Group VIIb element to a Group b alloy.

[Action]

The stability of the pinhole over time depends on the characteristics of the IIIb-IVb group.
It is ensured by the viscosity lowering effect at the time of alloy melting by the addition of group b.

〔Example〕

In the figure, reference numeral 10 denotes a mask semiconductor laser according to the present invention.

The mask semiconductor laser 10 has a semiconductor laser 11, a transparent insulating layer 12, and a mask layer 13, and the mask layer 13 has a pinhole as an emission hole by the radiation light of the semiconductor laser 11 itself.
PH is formed.

Various types of semiconductor lasers 11 can be used without particular limitation.

The transparent insulating layer 12 also functions as a protective layer and an insulating layer for the semiconductor laser 11, and for example, SiO, SiO ₂ , Si ₃ N ₄ or the like is used.

 Hereinafter, a description will be given in accordance with a specific experimental example.

In each of the following examples and comparative examples, a (GaAl) As-based double hetero type laser was used as the semiconductor laser 11 serving as a base. The maximum rated output of this semiconductor laser was 5 mW, the continuous operation output was 3 mW, and the oscillation wavelength was 780 nm. On the Fabry-Perot cavity mirror surface of this semiconductor laser, for example, a silicon nitride film is used as the transparent insulating layer 12. The one formed with a thickness of

Then, a pinhole PH was formed for each material using various materials as the mask layer 13, and the formation conditions and the formation results are shown in the table as described below so that they can be compared.

Note that the aperture injection current during the formation of the pinhole PH is the value that captures the same change in the monimer current when the injection current of the semiconductor laser is gradually increased and suddenly changes with the formation of the pinhole. And Observation of the shape and accuracy of the pinhole PH was performed using a scanning electron microscope.

Experimental Example 1 Cu was deposited on a transparent insulating layer 12 of Si ₃ N ₄ formed on a Fabry-Perot mirror surface of an (Al—Ge) As semiconductor laser.
When the mask layer 13 was formed by a vacuum evaporation method using an alloy having a composition ratio of Al ₂₉ Ge ₇₀ Cu ₁ added with 0 wt%, the film thickness at this time was 3500A. The deposition conditions at that time are described below.

Deposition source temperature: 1200 ° C Temperature Deposition source boat: Tungsten Vacuum degree: about 1 × 10 ^-5 torr Substrate temperature: 20 ° C to 40 ° C Next, a semiconductor laser is turned on to form a pinhole. When the monitor power supply was observed while increasing it, the monitor current suddenly changed at an injection current of 72 mA. When observed with an electron microscope, a sharp and nearly circular pinhole of 0.9 μm × 0.8 μm was obtained.

Then, it was evaluated whether or not the influence of Cu has a temporal expansion of the pinhole diameter with respect to the mask layer 13 when the laser is continuously lit and the oxidation resistance.

For comparison, the mask layer formed of Ge and Al
The characteristics described above were also evaluated for those formed of a -Ge alloy (70 wt% Ge).

 The evaluation method is as follows.

Oxidation resistance is 1% in a thermostatic chamber adjusted to 60 ℃ and 80% RH.
After storage for 4 days and 32 days, the state of oxidation was observed visually and by X-ray diffraction.

To grasp the change over time of the pinhole, use the semiconductor laser 11.
After turning on for 500 hours, the pinhole diameter was observed with a scanning electron microscope.

 The results are summarized in Table I below.

From Table I, it was confirmed that when the mask layer was made of a material obtained by adding Cu to the Al-Ge alloy, the pinhole opening state had less residue and the sharpness was improved as compared with the Al-Ge alloy. Was done. On the other hand, it was found that the oxidation resistance and the change with time of the pinhole diameter were almost the same as those of the Al-Ge system.

Experimental Example 2 In the same manner as in Experimental Example 1, a mask layer having a composition ratio of Al ₂₉ Ge ₇₀ Ag ₁ to which 1 wt% of Ag was added was provided by vacuum evaporation. The results are shown in Table II below.

As shown in Table II, the mask layer made of a material obtained by adding Ag to an Al-Ge alloy has an improved hole opening state as in Experimental Example 1, and the oxidation resistance and the change with time of the pinhole diameter are also Al-Ge based. It was confirmed that it had almost the same characteristics as.

Experimental Example 3 In this experimental example, chlorine in halogen was selected as an additive to the Al-Ge alloy. The added amount is 0.5 wt%. Therefore, the alloy composition was Al _29.5 Ge ₇₀ Cl _0.5 , and a mask layer was prepared and evaluated using this material according to Experimental Examples 1 and 2. The results are shown in Table III below.

From Table III, the mask layer made of a material obtained by adding Cl to the Al-Ge alloy had a hole shape similar to that of Experimental Examples 1 and 2, with little residue and close to a sharp circular shape. However, although the oxidation resistance tends to be slightly reduced, it can be improved by changing the alloy composition ratio.

As described above, from Experimental Examples 1, 2, and 3, the IIIb-IVb
It was confirmed that by using an alloy to which a group I element was added as a mask layer material, it was possible to make the pinhole opening state free of residue and sharp.

Thus, a group IIIb-IVb alloy may have a group Ib element such as
If an alloy containing Cu, Ag or the like or a VIIb group element such as Cl is used as the mask layer material, the aperture state of the pinhole portion of the mask semiconductor laser is reduced to a residue, and a state close to a sharp circular shape. can do. This is presumably because the addition of these elements lowers the viscosity of the alloy during melting. That is, an alloy containing these elements, for example, a Cu-Al-Ge alloy is provided as a mask layer by a vacuum evaporation method, and the semiconductor laser is turned on to heat and melt the mask layer to form a pinhole. ,
At this time, as the viscosity of the alloy at the time of melting is lower, fly-off, that is, less residue, and sharper opening are more likely to be obtained. In order to realize this viscosity reduction, two methods are conceivable.

To lower the melting point of a material. This utilizes the phenomenon that the viscosity of a liquid generally decreases with increasing temperature.

The structure is changed at the melting point of the material to lower the viscosity.

Among these, the present invention has obtained the desired effect by the method described below.

〔The invention's effect〕

According to the present invention, it is possible to relatively easily form a pinhole with the radiation light of the semiconductor laser itself without causing a temporal change in the pinhole accuracy, and to obtain a mask semiconductor having a good processing accuracy.

[Brief description of the drawings]

The figure is a perspective view of a mask semiconductor laser to which the present invention is applied. 13 Mask layer.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masato Hariya 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Ide ▲ Yasushi ▼ 1-3-3 Nakamagome, Ota-ku, Tokyo No. 6 Inside Ricoh Company, Ltd. (56) References JP-A-63-34991 (JP, A) JP-A-63-198390 (JP, A) JP-A-57-6266 (JP, U) JP-A-62 52962 (JP, U)

Claims (1)

(57) [Claims] 1. A mask semiconductor laser having a mask layer for shielding light emitted from a semiconductor laser, wherein said layer is provided with an emission hole for said emitted light. A mask semiconductor laser comprising a material to which a group b or VIIb element is added as the mask layer.