NONEQUILIBRIUM MODES OF OPERATION OF NARROW-GAP SEMICONDUCTOR-DEVICES

Research work is reviewed which uses the phenomena of minority carrier extraction and minority carrier exclusion to reduce the carrier densities in narrow-gap Hg1-xCdxTe alloys to near-extrinsic values at temperatures where the materials are normally intrinsic. This is of particular interest for the suppression of Auger noise which otherwise severely limits the performance achievable from infrared detectors at near-ambient operating temperatures. Improved performance has been obtained from excluding photoconductive detectors at modulation frequencies above 10 kHz. Theoretical work predicts improved performance from heterojunction extracting diodes. Early experiments on 'proximity-extracting' diode structures show large reductions in leakage current at intermediate and ambient temperatures compared to non-extracted diodes, but the residual current is higher than that predicted from Shockley-Read generation. Bipolar transistor action is observed at temperatures where the material is near-intrinsic in equilibrium. The transistor characteristics are strongly influenced by electron impact ionisation.