High pressure studies on infrared detector materials

The mercury chalcogenides HgTe, Hg1-x QH Te and the lead chal-cogenides Pb1 Sn Te have received considerable attention in recent years because of their use in infrared photon detectors. This article deals with the pressure studies on the sYmmetry induced zero gap semiconductors13; belonging to the zinc blend family viz., HgSe, HgTe and13; Hg1 Cd Te and the pressure induced semidonductor- semiconductor transition in Pb1-x,Sn Te.proposed by Groves and Paul (1963) is valid for HgTe, the conclusions It is shown that although the inverted band model of the earlier workers on the pressure induced f6 fa crossover are13; erroneous. Experimental results show that it is difficult to observe the band crossover due to an intervening structural phase transition from the zinc blend to the cinnabar structure. However, the present pressure experiments on the semiconductor alloy system Hg 0.9 C dO. 1 Te clearly indicate this crossover transition. Thermoelectric power and13; resisti vity data on PbO. 8 snO. 2 Te indicate that the principal energy gap E = E - - E + decreases with pressure resulting in a zero gap g L6 L6 . state near 35 -Kbar pressure. TEP studies on the alloy system PbO.6 SnO.4 Te provide direct evidence for a pressure induced L6+ L6+13; crossover transition