Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – In combination with or also constituting light responsive...
Reexamination Certificate
1999-06-09
2001-06-26
Mintel, William (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
In combination with or also constituting light responsive...
C257S082000, C257S184000, C257S458000, C257S461000, C257S465000, C257S466000
Reexamination Certificate
active
06252251
ABSTRACT:
BACKGROUND OF THE INTENTION
1. Field of the Invention
The present invention relates to semiconductor devices and, more particularly, to a raised photodetector having a channel for guiding light therethrough and a light responsive region recessed within the channel for detecting light.
2. Description of the Related Art
The development of integrated optical circuits has become the subject of increased interest in the field of telecommunications. For example, feedback control of lasers in an optical system is of paramount importance as users demand more and more reliable data transmission for a given bandwidth. However, a number of difficulties have been encountered in monitoring lasers, as the monitoring mechanism itself introduces unacceptable signal losses to the optical system.
Prior art techniques require the positioning of a beam splitter along the propagation path of light from a laser so as to divert a portion of the laser light for feedback monitoring. Beam splitters may for example be constructed of dichroic mirrors, i.e. mirrors which transmit one wavelength or a range of wavelengths and reflect the remaining wavelengths. Alternatively, they may be constructed of partially reflecting mirrors which reflect a portion of the incident light and transmit the remaining portion. In any event, such beam splitting causes the output beam from the lasers to incur signal losses that are unacceptable in optical communication applications. Furthermore, beam splitters undesirably increase the number of parts in an optical system and add to its complexity, thereby increasing the cost of the system.
Accordingly, there is a need for a compact, low-cost light detecting device for monitoring light from a laser without requiring the use of a beam splitter.
SUMMARY OF THE INVENTION
It is a therefore an object of the invention to provide a photodetector which can monitor light emitted from a laser without requiring use of a beam splitter.
In accordance with a presently preferred embodiment of the invention, a raised photodetector is constructed so as to define a groove or channel extending between opposite edges of the photodetector and dimensioned for permitting a beam of light to pass therethrough. The photodetector has a light-collecting region disposed centrally in an outward facing wall recessed within the groove or channel for collecting light from an adjacent laser. Preferably, the walls defining the channel have an anti-reflection coating or film deposited thereon.
A preferred embodiment of the inventive method includes the steps of providing an InP substrate having a first side and a second side; forming an InP buffer layer on the first side of the InP substrate; forming a light absorbing layer of InGaAs on the InP buffer layer; forming another InP layer on the light absorbing layer; selectively masking said another InP layer so as to define an unmasked area having a preselected width and extending between opposite edges of the InP substrate; etching the unmasked area so as to form a channel extending through said another InP layer and having a preselected depth h; forming a light collecting region in said another InP layer and the light absorbing layer; forming an anti-reflection film on the walls defining the channel; forming a p side electrode on said another InP layer; and forming an n side electrode on the second side of the substrate.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.
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Bylsma Richard Bendicks
Rinaudo Dominic Paul
Schlenker Rory Keene
Shakespeare Walter Jeffrey
Lucent Technologies - Inc.
Mintel William
LandOfFree
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