Detectors 185
Detectors 185 : Particle Detectors: (4.24) Resonant-Cavity-Enhanced Photo Detector: (3) Material Requirements for RCE Devices: The estimated superior performance of the RCE devices critically depends on the realization of very low loss active region. This enforces the conditions that: the mirror and the cavity materials must be non-absorbing at the detection wavelength; and the mirror should have very high reflectivity so that it gives highest optical confinement inside the cavity. The absorption in the cavity can be limited by making the bandgap of the active region smaller than the cavity and the mirror. But a large difference in the bandgap would be a blockage in extraction of photo generated carriers from a heterojunction. Usually a moderate offset is kept within the absorption spectrum. Different material combinations satisfy all of the above criteria and are therefore usable to the RCE scheme. Some material combinations used for RCE detection are: (a) 1. GaAs (M,C) / AlGaAs (M) / InGaAs (A) near 830-920nm. (b) 2. InP (C) / In0. 53Ga0. 47As (M) / In0. 52Al0. 48As (M) / In0. 53-0. 7GaAs (A) near 1550nm. (c) 3. GaAs (M,C) / AlAs (M) / Ge (A) near 830-920nm. (d) 4. Si (M,C) / SiGe (M) / Ge (A) near 1550nm. (e) 5. GaP (M) / AlP (M) / Si (A,S) near visible region
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