Radiant energy – Invisible radiant energy responsive electric signalling – Semiconductor system
Reexamination Certificate
2005-10-13
2009-10-27
Porta, David P (Department: 2884)
Radiant energy
Invisible radiant energy responsive electric signalling
Semiconductor system
C250S338400
Reexamination Certificate
active
07608830
ABSTRACT:
A photodiode for detection of preferably infrared radiation capable of detecting two different wavelengths wherein photons are absorbed in one region and detected in another. In one example embodiment, an absorbing P region is abutted with an N region of lower doping such that the depletion region is substantially (preferably completely) confined to the N region. The N region is also chosen with a larger bandgap than the P region, with compositional grading of a region of the N region near the P region. This compositional grading mitigates the potential barrier between the respective bandgaps. Under first voltage conditions a potential barrier prevents minority carriers from moving from the P region to the N region, but photons of energy large enough to generate minority carriers within the N region are detected. Under reverse bias, the barrier is substantially reduced or disappears, allowing charge carriers to move from the absorbing P region into the N region (and beyond) where they are detected. Thus, under reverse bias, both wavelengths of energy can be detected, and separated by differencing the output.
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DRS Sensors & Targeting Systems, Inc.
Igyarto Carolyn
Porta David P
Sonnenschein Nath & Rosenthal LLP
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