Silicon p-i-n Photodetector Using Internal Reflection Method

Abstract

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 multiple-reflected in the detector so that a long distanse is traveled and most of the photon energy is absorbed by the detector. The photodetector is particularly useful in detection of light with wavelengths near the instrinsic absorption edge. Theoretical analysis of photoresponse for a p-i-n pphotodetector is presented. Both the steady-state and time-dependent responses are derived; and the two important limiting cases with zero and infinite surface recombination velicities are taken as examples to illustrate the photoresponse. The photodetectors are fabricated from 4,000Ω-cm, n-type, <111>oriented silicon wafers. Both sides of the wafer are polished with one side inclined 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 um and 1.1 um (with absorption coefficients of 100 cm-1 and 3 cm-1 respectively) are in reasonable agreement with the theoretical prediction.