Active solid-state devices (e.g. – transistors – solid-state diode – Heterojunction device – Field effect transistor
Reexamination Certificate
2005-11-30
2008-09-02
Luu, Chuong A. (Department: 2892)
Active solid-state devices (e.g., transistors, solid-state diode
Heterojunction device
Field effect transistor
C257S019000, C257S184000, C257S187000
Reexamination Certificate
active
07420225
ABSTRACT:
A direct detector for terahertz radiation comprises a grating-gated field-effect transistor with one or more quantum wells that provide a two-dimensional electron gas in the channel region. The grating gate can be a split-grating gate having at least one finger that can be individually biased. Biasing an individual finger of the split-grating gate to near pinch-off greatly increases the detector's resonant response magnitude over prior QW FET detectors while maintaining frequency selectivity. The split-grating-gated QW FET shows a tunable resonant plasmon response to FIR radiation that makes possible an electrically sweepable spectrometer-on-a-chip with no moving mechanical optical parts. Further, the narrow spectral response and signal-to-noise are adequate for use of the split-grating-gated QW FET in a passive, multispectral terahertz imaging system. The detector can be operated in a photoconductive or a photovoltaic mode. Other embodiments include uniform front and back gates to independently vary the carrier densities in the channel region, a thinned substrate to increase bolometric responsivity, and a resistive shunt to connect the fingers of the grating gate in parallel and provide a uniform gate-channel voltage along the length of the channel to increase the responsivity and improve the spectral resolution.
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Allen S. James
Lee Mark
Shaner Eric A.
Wanke Michael C.
Bieg Kevin W.
Luu Chuong A.
Sandia Corporation
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