Silicon p-i-n photodetector using internal reflection method

A semiconductor photodetector is proposed which makes use of an internal reflection method to enhance the photoresponse. This method is to let the incident light be multiply-reflected in the detector so that a long distance is traveled and most of the photon energy is absorbed by the detector. Theoretical analysis of the steady-state and time-dependent photoresponses for a p-i-n photodetector is presented. The photodetector is found to be particularly useful in detection of light with wavelengths near the intrinsic absorption edge. The photodetectors are fabricated from 4000 Ω.cm n-type, oriented silicon wafers. Both sides of the wafer are polished with one side inclined one-half degree with respect to the other. The p+n junction and the ohmic contact are formed by alloy method. The measured photoresponses for wavelengths of 1.0 and 1.1 µm are in reasonable agreement with the theoretical predictions.