JPS62115792A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To realize a practically usable laser element whose end faces are produced through working processes other than the cleavage process, by coating the laser element unsymmetrically such that the auxiliary end face used only for monitor light or the like has a larger difference in level than the other end face. CONSTITUTION:End faces of light emission output surface are produced by wet etching and dry etching. In each of these end faces, levels are differed between the surface of the light emitting region and the surface of the other region. The difference in level (difference 1) between the light emitting region and the other region in the principal light emission end face is smaller than the difference in level (difference 2) between the light emitting region and the other region in the other end face. The difference 1 is 5mum or less, while the difference 2 is 10mum or less. A low reflection film 6 is provided on the end face with the smaller difference in level. A high reflection film 8 is provided on the end face with larger difference in level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an element shape of a semiconductor laser device, and particularly to an element shape suitable for mass production and packaging.

[Background of the invention]

Recently, wet etching methods other than the cleavage method have been applied to the end face of semiconductor lasers (Wada et al., Proceedings of the 1985 Autumn Conference of Japan Society of Applied Physics, 13p-R-5, and Shibuya et al., IEICE Technology E).
D-84-95, page 75) and dry processing method (see page 75)
Japanese Journal of Applied Physics, Volume 24, 1985, Page L463 (S,
Semura at al, J, J, A, P, Vol.
, 24. There are reports of processing examples according to PL463.1985), but these are still in the experimental stage and only one end surface is processed.

[Purpose of the invention]

An object of the present invention is to provide an element structure suitable for mounting a semiconductor laser whose end face is manufactured by a processing method other than cleaving.

[Summary of the invention]

When the end face of a semiconductor laser is fabricated by processing other than the cleavage method, a step is created between the substrate and the processed surface due to etching, and a portion of the emitted light is reflected by this step, resulting in F ar −F 1eldP attern during mounting.
disturbance occurs. The present invention solves this problem by creating an element structure in which the step on the end surface side, where light is used effectively, is reduced, and the step on the end surface side, which is used only for monitoring light, is increased.

Additionally, a low-reflection coating was applied to the end face, which has fewer steps and is used more effectively for light, and a high-reflection film was coated to the end face, which has a larger step and is only used as a monitor light. This problem was solved by creating an element structure with an asymmetric coating.

[Embodiments of the invention]

This example will be described in detail below.

Example 1 A semiconductor laser will be explained using an example having a Gat-xAQllAl1 duffle heterojunction structure. As shown in FIG. 1, G ax-J Q
An XAs double heterojunction epitaxial crystal 2 is grown, and a P-type electrode 3. An n-type electrode 4 was attached. Next, a photoresist is applied onto the p-type electrode 3, and a pattern in the end surface processing area is printed and developed using photolithography. Through the steps up to this point, a band-shaped photoresist film 5 is formed. Next, the p-type electrode 3 is removed by etching with a solution of ceric ammonium nitrate:water=1:10 using the photoresist 5 as a mask.

An example of end face processing using aet etching will be described. Double heterocrystal 2 was mixed with sulfuric acid: hydrogen peroxide: water (1
Etch to a depth that reaches the substrate crystal 1 at an etch center of: 5:1). In this process, a nearly vertical groove is completed, which will serve as the end surface for extracting the laser's light emission output.

Next, the photoresist 5 that is no longer needed is removed.

Next, as shown in FIG. 2, a scratch is made by applying the tip 11 of the scriber to a flat part provided at the end of the wafer and on an extension line (indicated by a dotted line) on one side of the groove formed on the end surface. This is done for each groove and the wafer is bent to form strip-shaped elements.

Furthermore, a single element is completed by scribing in a direction perpendicular to the groove. FIG. 3 shows the device after completing the steps up to this point.

The above describes a wet etching method as an end face processing method, but a dry etching method is also possible.In order to increase the dry etch resistance of the photoresist 5, the wafer shown in FIG.
t) Irradiate with light and then bake at 180°C. This sample was subjected to E CR (E 1 ectron cycle).
otron Re5onance) RIB using discharge
E(Reactive Ion Baam Etchi)
ng) The device is set, and CQz gas is introduced and discharged to perform etching to a depth that reaches the substrate crystal 1. The subsequent steps are the same as those described for wet etching above.

However, the photoresist 5 is removed using an Oz plasma asher.

FIG. 4(a) shows the front view of the laser device shown in FIG. 3 from the end face side with fewer steps, that is, from the left side. Figure 4(b) shows the Far Field Pattern from the right end face side with a large step.
Shown below. As you can see, F ar F 1 on one side
eld Pattern has no disturbance at all, and the other Far Field Pattern has disturbance. When a semiconductor laser is mounted and used in a system, if it is assembled and used so that the end face side with fewer steps is the side that actually uses light effectively, no problems will occur and it will be possible to put a laser element whose end face is formed by processing into practical use. Problem resolved.

Although this embodiment has been described with reference to the Ga t-J 11 XA9 double heterostructure, the crystal material is not limited in any way. Furthermore, regarding the structure of the laser element, CSP
(Channelad 5ubstrate Pla
ner) type, B H (B uriad Hetsros
It is obvious that the present invention is possible with any type of semiconductor laser device, such as a laser diode (structure) type or a variety of other semiconductor laser devices.

Example 2 As in Example 1, the conductor laser is G a 1-xA Q
This will be explained using an example having an XAs double heterojunction structure. As shown in FIG.
t-xA Q XAs double heterojunction epitaxial crystal 2 is grown, p-type electrode 3. Ni electrode 4 was attached.

Next, a photoresist is applied onto the p-type electrode 3, and a pattern of the end surface processing area is printed and developed using photolithography. In the steps up to this point, a band-shaped photoresist [5] is formed. Next, the p-type electrode 3 is formed using the photoresist 5 as a mask, and the mixture is ceric ammonium nitrate:water=1:1.
Remove by etching with 0 solution.

An example of end face processing using wet etching will be described. Double heterocrystal 2 was mixed with sulfuric acid: hydrogen peroxide: water (1
:5: Etching is performed using an etchant of 1) to a depth that reaches the substrate crystal 1. In this process, a nearly vertical groove is completed, which will become the end face for extracting the laser's light output.

Next, the photoresist 5 that is no longer needed is removed.

The above describes a wet etching method as an edge processing method, but a dry etching method is also possible.In order to increase the dry etching resistance of the photoresist 5, the wafer shown in FIG.
) Irradiate with light and then bake at 180°C. This sample was subjected to ECR (Electron Cyclot
RIBE using discharge (ron Re5onance)
(Reactive I on Beam Etc
hing), and the CQ 2 scum is introduced and discharged to a depth that reaches the substrate crystal 1. In this process, a nearly vertical groove is completed, which will become the end face for extracting the laser's light output. Next, the unnecessary photoresist 5 is removed using an OX plasma asher device.

The wafer that has undergone the steps up to this point is placed in a vacuum evaporation device for the purpose of depositing a low-reflection film, and 5iOz is deposited on the end face from an angle to the wafer at a p/4 n 1 concentration using electron beam evaporation as shown in Figure 5. to adhere to.

Here, P is the oscillation wavelength of the laser, and nl is the refractive index of 5iOz. In FIG. 5, 7 is a schematic drawing of a 5i (h particle), and 6 represents a 5iOz film deposited on the end face and the electrode 3 of the wafer. As shown in the figure, 5iOz was applied to the end surface opposite to the end surface coated with the low reflection film for λ/4nt, and then Si was applied for λ/4nt.
4n2 deposited. Here, n2 is the refractive index of Si. In FIG. 6, 9 schematically represents particles of 5LOz and Si, and 8 represents a high reflection film made of 5xOz+Sx.

Next, as shown in FIG. 7, the grooves on the processed end surface are filled with photoresist 10 using photolithography technology.
Unnecessary insulating films 6 and 8 deposited on the p-type electrode 3 are removed with HF:N.
Remove with H No. F (1:6) etching solution. Thereafter, the photoresist 10 is removed.

Next, as shown in FIG. 8, a scratch is made by applying the tip of a scriber to a flat part provided at the end of the wafer and on an extension line (indicated by a dotted line) on one side of the groove formed on the end surface. This is done for each groove and the wafer is bent to form strip-shaped elements. Furthermore, a single element is completed by scribing in a direction perpendicular to the groove. The device that has completed the steps up to this point is the 9th
As shown in the figure.

12 shows an example of the optical output from the end face side with fewer steps, that is, the low reflection side of the laser element shown in FIG. 9. In addition, the example of F ar F 1eld P atttern is shown in the fourth example.
The result will be similar to that shown in Figure (a). An example of the light output from the end face side with a large step difference, that is, the high reflection film side is shown in 13 in Fig. 10, and F
The example of ar F eld P attern is similar to that shown in FIG. 4(b). As you can see, a large light output is emitted from one side, and F ar F 1eld P
Attern is not disturbed at all, and the light output from the other is small.

Moreover, the disturbance affects the F ar F eld P attern.

When a semiconductor laser is mounted and used in a system, if it is assembled and used so that the low-reflection film side is the side that actually uses light effectively, no problems will occur. The problem of putting the laser device into practical use has been solved.

Although this embodiment has been described with respect to a Ga 1-XA Q Js double heterostructure, the crystal material is not limited in any way. Furthermore, regarding the structure of the laser element, CSP
(Channeled 5ubtrate Plana
r) type, BH (B uriad Heterostru
It is also possible to use any type of semiconductor laser device, such as a 3D (curve) type or other types of semiconductor laser devices.

Although an example of processing both end faces has been described, it is similarly possible to process one end face and cleave the other end face. Furthermore, although the explanation has been given using examples of 5iOzλ/4ns as a low reflection film and high reflection films 5iOz and 5L2WJ, other materials such as AQxOδ may be used.

5iaN + amorphous Si or hydrogen-containing amorphous Si is also possible, the thickness of the low reflection film is slightly deviated from λ/4nx, and a 4-layer film is also possible as a high reflection film. Further, although the explanation has been given on the case where the wafer is coated with an amorphous material, it is clear that it is also possible to coat the device with an amorphous material after it has been formed into a strip or a chip.

〔Effect of the invention〕

When a wafer of a laser device whose both end faces are fabricated by a processing method other than cleavage is turned into chips in a crosswise manner, a difference in level between the cut surface and the end face processed surface at the time of chip formation occurs on both end faces. Therefore, disturbance occurs in the F ar F 1eldP attern on both sides, but in the present invention, the chip is intentionally cut so that this level difference occurs only on one side.
This structure suppresses the disturbance of the LD pattern to only one end face, and when a semiconductor laser is mounted in a system, the structure is convenient for applications in which only one side actually uses light effectively, and the processing method This has the effect of making it possible to put into practical use a laser device whose end facets are fabricated using the method described above.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a semiconductor laser wafer showing an embodiment of the present invention, Fig. 2 is a perspective view of a wafer whose end face has been processed and is being scribed, and Fig. 3 is a perspective view of a semiconductor laser element made into chips. Figure 4 is a far-field image of the emitted light from the laser element in Figure 3, Figure 5 is a cross-sectional view of a wafer whose end face has been processed and coated with a low-reflection film, and Figure 6 is a cross-sectional view of the wafer. Figure 7 is a cross-sectional view of the wafer being coated with a high-reflection film, Figure 7 is a cross-sectional view of the edges of the wafer edge groove filled with a photoresist film, Figure 8 is a perspective view of the wafer being scribed, Figure 9 The figure is a perspective view of a chipped semiconductor laser device, and FIG. 10 is a diagram showing an example of the electrical and optical characteristics of the laser device. 1- n-type GaAs substrate, 2- Gal-x A
Q x A s double hetero growth layer, 3...p-type electrode, 4...n-type electrode, 5...photoresist, 6...
- Low reflective film, 7... Particles for low reflective film, 8... High reflective film, 9... High reflective film particles, 10... Photoresist, 11... Tip of scribe.

Claims (1)

[Claims] 1. Both end faces of the light emitting output surface are created by wet etching and dry etching, and the end faces have a step between the light emitting region surface and the other region surface. In a semiconductor laser, the difference in level (step 1) between the light emitting region and the surface of the other region at the main light emitting end facet is smaller than the difference in step (step 2) between the light emitting region and the surface of the other region at the other end facet. A semiconductor laser featuring 2. The step 1 is 5 μm or less, and the step 2 is 10 μm or less.
2. The semiconductor laser according to claim 1, wherein the semiconductor laser has a diameter of μm or less. 3. In a semiconductor laser that has a step between the light emitting region surface and the other region surface on one end surface or both end surfaces forming the light emitting output surface of the semiconductor laser, a low reflection film is provided on the end surface with fewer steps. A semiconductor laser characterized by having a highly reflective film on an end face with many steps.