JPS6154688A - Semiconductor light-emitting device - Google Patents

Abstract

PURPOSE:To unify both semiconductor lasers for erasing and writing by forming the two semiconductor lasers, which are isolated so as to be able to be driven independently to each other and have different astigmatism, onto the same substrate. CONSTITUTION:Two semiconductor lasers LD1, LD2 are isolated by a groove 9. Since a striped active region 7A is exposed on a cleavage plane in the laser LD1, optically confined laser beams not only in the vertical direction but also in the lateral direction are radiated, thus forming a circular spot when the laser beams are diaphragmed by a lens. Since a striped acrive region 7B is broken on its midway and there is an inactive region 8 between the region 7B and a light rediating surface in the laser LD2, beams emitted from the region 7B form a pattern extended in the lateral direction, thus shaping an elliptic spot when beams are diaphragmed by the lens. Accordingly, the circular spot is obtained because of small astigmatism in the laser LD1, the elliptic spot is acquried because of large astigmatism in the laser LD2, and the former can be used for writing and the latter for erasing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor light emitting device suitable for use in optical information processing, such as writing and erasing on an optical disk.

[Conventional technology]

In recent years, optical disk devices have been viewed as promising as devices capable of large-capacity storage, and in particular, rewritable devices are expected to replace magnetic disk devices.

Normally, this type of optical disk device requires three semiconductor lasers for data writing, data reading, and data erasing.

It goes without saying that these three types of semiconductor lasers need to be placed at optically appropriate positions with respect to the optical disc. Therefore, the erasing semiconductor laser and the writing semiconductor laser must be placed close to each other.

Separately, in the writing semiconductor laser, it is necessary to focus the laser beam on the optical disk surface to around 0.5 [μm]φ, and in the erasing semiconductor laser, the minor axis is 0.5 [μm]φ. [μm] and long sleeves are 2 to 3 [μm]
] It is necessary to make it an ellipse.

The reason for this is that currently, attempts are being made to make rewritable optical discs compatible with binary data by taking advantage of the difference in light reflectance between crystalline and non-crystalline discs. When a possible substance is irradiated with a laser beam, melted, and then rapidly cooled, it becomes amorphous, so it is recorded as writing, and similarly, when it is melted and then slowly cooled, it becomes crystalline, so it is erased. The circular laser beam is required to perform this, and the elliptical laser beam is required to perform melting and slow cooling. Note that an elliptical laser beam is irradiated with its long axis in the direction of the trunk of the optical disk, and its short axis is in the track width direction.To avoid crosstalk, a circular laser beam is used. It must be approximately the same as the diameter in the light.

[Problem that the invention seeks to solve]

However, as mentioned above, it is complicated to arrange the three types of semiconductor lasers at optically appropriate positions with respect to the optical disk and to satisfy the requirements regarding the cross section of the luminous flux of the laser beam as mentioned above. This is extremely difficult because it requires a sophisticated optical system, and there is a particular problem in arranging the erasing semiconductor laser and the writing semiconductor laser close to each other.

Therefore, if at least the erasing semiconductor laser and the writing semiconductor laser can be integrated, the entire optical system will be extremely simple.

The present invention integrates a semiconductor laser for writing and a semiconductor laser for erasing, and also makes the cross section of the laser beam of the laser beam in the semiconductor laser for writing into a circular shape of, for example, about 0.5 [μm]. For example, the cross section of the beam of laser light in a semiconductor laser has a short axis of 0.5 [μm] and a long axis of 2 to 2.
To provide a semiconductor laser that can be formed into an ellipse of about 3 [μm].

[Means for solving problems]

In the semiconductor light emitting device of the present invention, two semiconductor lasers separated by, for example, a groove and having different astigmatism are provided on the same semiconductor substrate, and in one of the semiconductor lasers, the light emitting surface of the active region is The other semiconductor laser has a structure in which an inactive region exists between the active region and the arm opening.

[Effect]

One of the semiconductor lasers can emit laser light with a circular cross section, and the other semiconductor laser can emit laser light with an elliptical cross section.

Since these semiconductor lasers are formed on the same substrate, the optical process is extremely simplified when used for writing and erasing in an optical disk device.

〔Example〕

FIG. 1 shows a perspective view of essential parts of an embodiment of the present invention.

In the figure, 1 is an n-type GaAs substrate, 2 is an n-type AILo
, 45Gao, 5sAs crano layer, 3 is n-type Afi
o, +5Gao, 1IsAs active layer, 4 is n-type A'
o, a5G ao, 5sAs cladding layer, 5 is p-type A
E o, ++sG ao, 5sAs cladding layer, 6 is n-type GaAs cap layer, 7A and 7B are zinc (
Zn) active region by diffusion, 8 is an inactive region, 9 is a groove for separating two semiconductor lasers, 10 is an n-side electrode, 1
'LA and IIB represent p-side electrodes, LDI represents a semiconductor laser whose laser beam has a circular cross section, and LD2 represents a semiconductor laser whose laser beam has an elliptical cross section.

In the semiconductor laser LDI in this embodiment, the striped active region 7A in which Zn is diffused and has a high refractive index is exposed to the light emitting surface, that is, the arm opening surface, so that it can be used not only in the vertical direction but also in the vertical direction. Since the laser light is emitted with optical confinement in the lateral direction as well, when it is narrowed down with a lens, it becomes a circular spot.In addition, in the semiconductor laser LD2, the striped active region 7B is cut in the middle and does not meet the light emitting surface. Since there is an inactive region 8 in between, the light emitted from the active region 7B is not confined in the lateral direction, but forms a pattern that spreads in the lateral direction, and when this is narrowed down with a lens, it becomes an elliptical spot. It is.

The case of manufacturing this embodiment will be explained with reference to FIGS. 1 and 2. Incidentally, FIG. 2 shows a plan view of the main part of the semiconductor light emitting device at key points in the process.

(a) Molecular beam epitaxial growth (mo I'e c
By applying the ar beam epitaxy (MBE) method, a layer with a thickness of about 3 [μm] is formed on the substrate 1.
cladding layer 2, active layer 3 with a thickness of about 0.08 Cμm,
Talad layer 4 with a thickness of approximately 2 cm μm, and a thickness of approximately 0.5 μm.
A cladding layer 5 of ] and a cap layer 6 of approximately 0.3 [μm] in thickness are grown.

(bl chemical vapor deposition
.

By applying the ur deposition (CVD) method, a thickness of about 0 is deposited on the surface, as seen in Figure 2.
．． A silicon nitride (Si3N4) film 12 with a thickness of 3 [μm] is grown.

fc) By applying photolithography technology, as shown in FIG. 2, the silicon nitride film 12 is patterned to form two parallel striped windows 12A and 12A with a width of about 1 μm. 12B is formed.

The interval between these two wooden striped windows 12A and 12B is 1
0 to 15 [μm], and one window 12A is continuous, while the other window 12B is periodically interrupted.

+d+ By applying an appropriate impurity introduction method,
Zn is introduced using the silicon nitride film 12 having the windows 12A and 12B as a mask to form p-type active regions 7A and 7.
Form B. In this case, since the windows 12B' are periodically interrupted, Zn is not introduced into those portions, which become inactive regions 8.

As a result, pn junctions for confining current are formed on the striped side surfaces of active regions 7A and 7B.

After removing the silicon nitride film 12 used as a tel mask, chemical etching is performed to form a groove 9 between the two active regions 7A and 7B, thereby making them electrically independent.

ifl n-side electrode 10 and p-side electrode 11A for flowing current separately to the two active regions 7A and 7B.
” and form IIB.

(g) By forming folds in the non-active region 8,
A semiconductor light emitting device is obtained in which two semiconductor lasers LDI and LD2 are formed adjacently on the same substrate.

When a current is passed through the semiconductor lasers LDI and LD2 in the semiconductor light emitting device thus obtained, they oscillate separately.

At this time, since the semiconductor laser LDI in which the active region 7A exists up to the light emitting surface, that is, the interfold surface, has small astigmatism, a circular spot of about 0.5 [μm]φ can be obtained by focusing with a lens. In addition, since the semiconductor laser LD2 in which the inactive region 8 exists in the interfold plane has a large astigmatism, 0.5 [μ
An elliptical spot of approximately 2 to 3 μm can be obtained.

Therefore, the semiconductor laser LDI that can produce a circular spot can be used for writing, and the semiconductor laser LD2 that can produce an elliptical spot can be used for erasing. In that case, only one focusing lens is required. become.

〔Effect of the invention〕

The semiconductor light emitting device of the present invention has a configuration including two semiconductor lasers that are formed adjacent to each other on the same semiconductor substrate, are separated so that they can be driven independently, and have different astigmatisms. are taken.

Therefore, when writing on an optical disk, immediately after erasing is performed by driving a semiconductor laser that emits a laser beam with a large astigmatism, that is, an elliptical spot, the astigmatism is small, that is, a circular spot. Writing can be performed by driving a semiconductor laser that emits laser light, and since these semiconductor lasers are integrated, only one optical system is required to handle the two laser lights. The configuration is greatly simplified.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the main parts of an embodiment of the present invention, and FIG. 2 is a plan view of the main parts of a semiconductor light emitting device at important points in the process to explain the manufacturing of the embodiment shown in FIG. each represents. In the figure, 1 is an n-type GaAs substrate, 2 is an n-type A Il
o, 45G a O, 55A S cladding layer, 3 is n
type AlO, I5G ao, esAs active layer, 4 is n-type AAO, 45G ao, 5sAs cladding layer,
5 is p-type An! o, n5Gao, 5sAs cladding layer,
6 is an n-type GaAs cap layer, 7A and 7B are active regions formed by Zn diffusion, 8 is an inactive region, 9 is a trench for separating two semiconductor lasers, 10 is an n-side electrode, IIA and I
IB represents a p-side electrode, LDI represents a writing semiconductor laser that generates a circular spot laser beam, and LD2 represents an erasing semiconductor laser that generates an elliptical spot laser beam. Patent applicant: Fujitsu Ltd. Representative Patent Attorney: Shoji Aitani Representative Patent Attorney: Hiroshi Watanabe - =

Claims (1)

[Claims] A semiconductor light emitting device comprising two semiconductor lasers formed adjacently on the same semiconductor substrate, separated so that they can be driven independently, and having different astigmatism.