Photoresponse model for Si1spl minus/x/Ge/sub x//Si heterojunction internal photoemission infrared detector

A photoresponse model has been developed for the Si
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spl minus/x/Ge/sub x//Si heterojunction internal photoemission (HIP) infrared detector at wavelengths corresponding to photon energies less than the Fermi energy. A Si/sub 0.7/Ge/sub 0.3//Si HIP detector with a cutoff wavelength of 23 μm and an emission coefficient of 0.4 eV/sup /spl minus/1/ has been demonstrated. The model agrees with the measured detector response at /spl lambda/>8 μm. The potential barrier determined by the model is in close agreement (difference /spl sim/4 meV) with the potential barrier determined by the Richardson plot, compared to the discrepancies of 20-50 meV usually observed for PtSi Schottky detectors.