Coherent light generators – Particular active media – Semiconductor
Reexamination Certificate
2002-04-01
2003-11-11
Leung, Quyen (Department: 2828)
Coherent light generators
Particular active media
Semiconductor
C372S036000
Reexamination Certificate
active
06647042
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a laser device and particularly to a group-III nitride semiconductor laser device.
2. Description of the Related Art
In order to achieve an operation as a laser, an optical laser cavity comprising a pair of reflecting mirrors is required. In semiconductor laser devices (Fabry-Perot type) using such semiconductor crystal materials as GaAs, a multi-layer body including a laser structure is cleaved simultaneously with a GaAs crystal substrate and then this cleaved facet is used as a cavity mirror of the laser device.
As concerns a semiconductor laser device formed from group-III nitrides, sapphire is commonly used as the substrate. Since sapphire does not have a clear cleavage plane, the cavity mirror can hardly be formed by cleaving. Accordingly, the cavity mirror of the semiconductor laser devices is formed by dry etching such as reactive ion etching (RIE).
Sapphire is chemically very stable and is therefore etched little, so that a sapphire substrate
101
is left unetched after the dry etching process. As a result a terraced structure (a terrace portion
103
) is formed as extending beyond a cavity mirror
102
′ of a multi-layer body
102
formed from group-III nitrides, as shown in FIG.
1
. In such a case, a part of a laser light
104
is reflected by the terrace portion
103
, thereby a far-field pattern is formed as a plurality of spots in stead of a single spot. Thus, the semiconductor laser device
100
could not be used particularly as a light source for a optical storage device.
To overcome this problem, a method for transferring the multi-layer body onto a substrate which is highly cleavable and cleaving this sample to form the cavity mirror has been proposed. Specifically, the multi-layer body is formed on the sapphire substrate, and this sample is bonded onto a carrier substrate which is highly cleavable. After removing the sapphire substrate from the multi-layer body, the multi-layer body is cleaved along with the carrier substrate, thereby obtaining a laser device with a cleaved facet serving as the cavity mirror.
OBJECTS AND SUMMARY OF THE INVENTION
In the manufacturing process for the conventional semiconductor laser device
100
mentioned above, if there is even a slight misalignment between the carrier substrate
105
and the multi-layer body
102
which are glued together, as shown in
FIG. 2
, a cleaved facet
105
′ of the carrier substrate
105
is partially extended, in the shape of a “terrace”, beyond a cavity mirror
102
′ of the multi-layer body
102
. In such a case, even if a dielectric mirror stack is formed on the cavity mirror
102
′ by a sputtering technique, sufficiently high reflectivity cannot be obtained because the coating film thickness varies due to the terrace portion
103
′. As a result, sufficient optical characteristics as a laser device cannot be achieved. Furthermore, as mentioned earlier, part of the beam is reflected by the terrace portion
103
′, resulting in multiplication of the far-field pattern, causing practical problems.
It is therefore an object of the present invention to provide a group-III nitride semiconductor laser device with excellent optical characteristics, and a method for manufacturing the same without steps requiring high assembly precision.
REFERENCES:
patent: 4592059 (1986-05-01), Westermeier
patent: 5181216 (1993-01-01), Ackerman et al.
patent: 5294815 (1994-03-01), Iechi
patent: 5621746 (1997-04-01), Futatsugi et al.
patent: 5953581 (1999-09-01), Yamasaki et al.
patent: 100 22 879 (2000-12-01), None
patent: 0 593 031 (1994-04-01), None
patent: 1 014 520 (2000-06-01), None
patent: 63-208293 (1988-08-01), None
patent: 2-35788 (1990-02-01), None
Miyachi Mamoru
Ota Hiroyuki
Leung Quyen
Pioneer Corporation
Sughrue & Mion, PLLC
LandOfFree
Nitride semiconductor laser device and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Nitride semiconductor laser device and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nitride semiconductor laser device and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3153324