Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal – Including integrally formed optical element
Reexamination Certificate
2002-07-02
2004-02-17
Lebentritt, Michael S. (Department: 2824)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Including integrally formed optical element
C438S030000, C438S031000
Reexamination Certificate
active
06692980
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for fabricating a semiconductor photonic device, and more particularly, to a method for fabricating an integrated semiconductor photonic device in which an active waveguide and a passive waveguide are combined with each other on a substrate.
2. Description of the Related Art
When fabricating a semiconductor photonic device, a current confinement layer is fabricated generally by a method of forming a p
/p current confinement layer or a method of forming a current confinement layer of buried ridge strip (BRS) type. Using the method of forming a p
/p current confinement layer, it is possible to effectively block electric current. However, this method has the disadvantage of there being slight variations in the structure of the resulting semiconductor photonic devices, especially, when a waveguide of a top and bottom dual structure is manufactured by combining a waveguide with a mode-conversion type passive waveguide. That is, this method is disadvantageous regarding reproducibility, whereas the method of forming a BRS type current confinement layer is profitable regarding reproducibility.
FIGS. 1A through 1D
are views explaining a method of forming a BRS type current confinement layer, which is disclosed in U.S. Pat. No. 6,025,207. In detail, a buffer layer
11
, a guiding layer
12
, an intermediate layer
13
and an active layer
14
are sequentially deposited on a substrate
10
. Next, as shown in
FIG. 1B
, the active layer
14
is patterned in the form of a strip, and portions of the intermediate layer
13
, which are exposed due to the patterning of the active layer
14
, are also etched. Then, referring to
FIG. 1C
, resumption of epitaxial growth is used to bury the active layer
14
in the p-type clad layer
16
, and then a conductive layer
18
is deposited on the p-type clad layer
16
. Thereafter, an ion implantation mask
26
is formed on the conductive layer
18
, being aligned with respect to the active layer
14
. Next, ions are implanted into the p-type clad layer
16
so as to form ion-implanted regions
17
a
and
17
b
at the both sides of the active layer
14
. As a result, a current confinement layer, which is defined by a channel C, is formed between the ion-implanted regions
17
a
and
17
b.
Then, referring to
FIG. 1D
, the ion implantation mask
26
is removed to form a contact layer
20
on the conductive layer
18
.
The method of forming a BRS type current confinement layer is easy to fabricate a photonic device by performing resumption of epitaxial growth only once. Therefore, this method has reproducibility when semiconductor devices are fabricated. However, this method is not proper in fabricating a monolithic integrated semiconductor photonic device that is integrated with a passive waveguide. Specifically, when fabricating the monolithic integrated semiconductor photonic device, it is very important to effectively combine an active layer with a passive waveguide. However, the method of forming a BRS type current confinement layer requires a p-type clad layer basically, which would result in higher optical losses when the active layer is combined with the passive waveguide. Further, an ion implanter, which is very expensive, is required, thereby increasing manufacturing cost therefor.
To solve these problems, A. Labrousse et al. suggested that a passive waveguide be made in the form of a deep ridge and then coupled with a BRS type active layer, disclosed in their thesis entitled “First 20 Gbit/s All Optical Wavelength Conversion with an Integrated Active-Passive Mach/Zehnder Interferometer and Comparison with the Similar All-Active Device” which was introduced in OAA 2001, OWA2. However, a deep ridge-type passive waveguide has higher optical losses than a buried waveguide. Also, the structure of a deep-ridge-type passive waveguide is very different from that of a buried active waveguide. For this reason, a monolithic integrated semiconductor photonic device has low coupling coefficient at a portion where the deep-ridge-type passive waveguide is combined with the buried active waveguide.
SUMMARY OF THE INVENTION
To solve the above problem, it is an object of the present invention to provide a method of fabricating a monolithic integrated semiconductor photonic device by effectively combining an active waveguide and a passive waveguide with each other, and minimizing a loss of light therein.
To achieve the above object, there is provided a method of fabricating a monolithic integrated semiconductor photonic device that effectively combines an active waveguide and a passive waveguide, and minimizes an optical loss, including: forming an active layer of a strip shape and a passive layer of a strip shape, which is connected directly to the active layer, on a first conductive substrate; forming a non-doped clad layer around the passive layer so as to form a passive waveguide, and a buried ridge strip (BRS) type current confinement layer around the active layer without ion injection; and forming a second conductive current injection layer on the resultant structure having the current confinement layer so as to form an active waveguide coupled to the passive waveguide.
According to the present invention, it is possible to remarkably reduce an optical loss in a passive waveguide by forming a non-doped clad layer around a passive layer. Also, a current confinement layer can be formed around an active layer without implanting ions, so that expensive equipment such as an ion implanter is not required. In addition, the active waveguide can be effectively coupled with the passive waveguide.
REFERENCES:
patent: 5862168 (1999-01-01), Schilling et al.
patent: 6025207 (2000-02-01), Mersali et al.
patent: 6194240 (2001-02-01), Chiu et al.
patent: 6309904 (2001-10-01), Pommereau et al.
patent: 2002/0110170 (2002-08-01), Bouadma
IEEE Photonics Technology Letters, vol. 10, No. 4, Apr. 4, 1998, pp. 510-512.
First 20Gbit/s all optical wavelength conversion withan integrated active-passive Mach-Zehnder Interferometer and comparison with the similar all-active device, 3 pages.
Baek Yongsoon
Kim Sung-bock
Oh Kwang-ryong
Park Jung-woo
Blakely & Sokoloff, Taylor & Zafman
Electronics and Telecommunications Research Institute
Lebentritt Michael S.
Smith Brad
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