Quantum transport in narrow-gap semiconductors

Abstract

A review is given of recent advances in quantum magnetotransport and its application to narrow-gap semiconductors. The experiments discussed include magnetophonon and magnetoimpurity measurements. In the quest to obtain band-gaps further into the infrared region of the spectrum for optical communication purposes, a number of ternary and quaternary alloy systems are presently being developed. It is found with these systems that the momentum matrix element (P²) determining the effective mass, instead of being a linear function of alloy composition, shows pronounced bowing. The experiments with alloys have been extended to the Pb_1−xSn_xTe and Pb_1−xGexTe system where an additional complication occurs because the plasmon frequency is comparable with the phonon frequency. In contrast to magneto-optical experiments it is found that the resonance occurs at the screened phonon frequency. In the magnetoimpurity effect the carriers lose energy by exciting carriers trapped on shallow impurity levels into higher lying levels or into the nearest band.