Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With reflector – opaque mask – or optical element integral...
Reexamination Certificate
2002-01-16
2003-12-23
Nhu, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With reflector, opaque mask, or optical element integral...
C257S079000, C257S918000
Reexamination Certificate
active
06667496
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical semiconductor apparatus usable as optical pickups and optical interconnection, such as light-emitting and light-receiving semiconductor apparatuses provided with monolithically-integrated light-emitting and light-receiving devices, and its fabrication method.
2. Description of the Related Background Art
In the field of the large scale integration (LSI), problems of signal delay in the electric wire, limitation to the transmission distance, and electromagnetic interference (EMI) between electric wires occur. Accordingly, there are limitations to improvements in high-density integration and large capacity. In sharp contrast thereto, the optical interconnection is advantageous in transmission speed, parallel transmission, and EMI-free characteristics. Therefore, the optical interconnection has been researched and developed as promising technology for solving those problems. Further, this technology has been studied to monolithically integrate light-emitting and light-receiving devices on a common substrate for use in the optical interconnection to reduce implementation cost and size.
Particularly, the following light-emitting and light-receiving apparatus is being watched with keen interest since a structure with a fine pitch can be readily fabricated and the degree of its layout is large. In this apparatus, a vertical cavity surface emitting laser (VCSEL) capable of emitting light perpendicularly to a substrate is used as a light-emitting device, a photodiode with a resonator of the same structure as that of the vertical cavity surface emitting laser is used as a light-receiving device, and these devices are monolithically integrated on the substrate. This apparatus, however, has the disadvantage that when the resonator of the surface emitting laser with a very high reflectivity is used in the photodiode without any modification, a wavelength bandwidth of the light-receiving sensitivity of the photodiode is narrowed due to too strong a wavelength sensitivity. Therefore, the reflectivity of the resonator in the photodiode is lowered to solve this problem.
An example is disclosed in “Electronics Letters, Jun. 20, 1996 Vol. 32 No. 13 pp. 1205-1207” In this example, as illustrated in
FIG. 1
, a lower semiconductor multi-layer mirror
1003
, an active layer
1005
having a multiple quantum well structure (this layer acts as an absorptive layer in a photodiode region
1000
B), and an upper semiconductor multi-layer mirror
1007
are grown on a semiconductor substrate
1001
. An upper portion of the upper multi-layer mirror
1007
in the photodiode region
1000
B is chemically etched to optimize the light-receiving sensitivity and detection wavelength bandwidth of the photodiode region
1000
B, while the upper multi-layer mirror
1007
in a light-emitting device region
1000
A remains unchanged.
Another example is disclosed in Japanese Patent Application Laid-Open No. 5(1993)-299689. In this example, as illustrated in
FIG. 2
, lower semiconductor multi-layer mirrors
1103
A and
1103
B, an active layer
1105
(this layer acts as an absorptive layer in a photodiode region
1100
B), and an upper semiconductor multi-layer mirror
1107
are grown on a semiconductor substrate
1101
. A spacer layer
1109
having a predetermined thickness is interposed between the lower semiconductor multi-layer mirrors
1103
A and
1103
B only in the photodiode region
1100
B to adjust the reflectivity of the lower semiconductor multi-layer mirrors
1103
A and
1103
B and to optimize the light-receiving sensitivity and detection wavelength bandwidth of the light-receiving device region
1100
B, while the lower semiconductor multi-layer mirrors
1103
A and
1103
B in a light-emitting device region
1100
A remain unchanged.
In the structure of
FIG. 1
, although the etching should be stopped at a predetermined location, the etching amount varies at different positions due to an in-surface distribution of the etching speed. A difference in the etching amount influences a phase in the reflection, and hence the light-receiving sensitivity and wavelength bandwidth vary among different devices. Accordingly, it is difficult to obtain devices having the same characteristics and to achieve a good yield.
In the structure of
FIG. 2
, since the spacer layer
1109
is inserted, regrowth of the spacer layer
1109
and other layers needs to be conducted after growth of the lower multi-layer semiconductor mirror is once interrupted and processes of photolithography, etching, and so forth are performed. Accordingly the fabrication process becomes complicated. Further, devices cannot be freely arranged since locations of light-emitting and light-receiving devices are determined at the stage of the growth.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical semiconductor apparatus in which a surface light-emitting device, such as a surface emitting laser and a surface light emitting diode (LED), and a surface light-receiving device having a wide detection wavelength bandwidth are integrated with a flexible combination of these devices, and a method for readily fabricating the optical semiconductor apparatus with good yield.
The present invention is generally directed to an optical semiconductor apparatus provided with a surface light-emitting device and a surface light-receiving device, which includes an active layer, a first spacer layer, and a first semiconductor multi-layer mirror. The active layer, the first spacer layer, and the first semiconductor multi-layer mirror are layered in a layering direction. A first region of the surface light-emitting device and a second region of the surface light-receiving device are arranged in a direction approximately perpendicular to the layering direction, the first region is electrically separated from the second region substantially, and the first spacer layer in the first region and the first spacer layer in the second region are subjected to different oxidization including non-oxidization, respectively, such that resonators composed of the first semiconductor multi-layer mirror and the first spacer layer in the surface light-emitting device and the surface light-receiving device have different wavelength dependencies of reflectivity, respectively. According to such a structure, the optical semiconductor apparatus can be readily achieved with good yield by a selective oxidization performed after a wafer having a desired configuration is fabricated.
Specifically, the first spacer layer is inserted in the first semiconductor multi-layer mirror. The first spacer layer is typically composed of at least a semiconductor layer containing aluminum (Al).
In one case, the first spacer layer in the first region is subjected to non-oxidization, and the first spacer layer in the second region is subjected to oxidization. In this case, the first spacer layer can be composed of a plurality of semiconductor layers, thicknesses and compositions of which are determined such that a resonator composed of the non-oxidized first spacer layer and the first semiconductor multi-layer mirror in the first region is under a non-resonance condition, or creates a maximum reflectivity, for light of a predetermined wavelength. Further, the thicknesses and compositions of the semiconductor layers in the first spacer layer can be determined such that a resonator composed of the oxidized first spacer layer and the first semiconductor multi-layer mirror in the second region is under a resonance condition, or creates a maximum transmissivity, for light of a predetermined wavelength.
In another case, the first spacer layer in the first region is subjected to oxidization, and the first spacer layer in the second region is subjected to non-oxidization. In this case, the first spacer layer can be composed of a plurality of semiconductor layers, thicknesses and compositions of which are determined such that a resonator composed of the oxidized first spacer layer and the first semiconducto
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nhu David
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