Photo-Hall investigation ofp-type HgTe-CdTe superlattices

We discuss detailed transport and phototransport measurements on a p-type HgTe-CdTe superlattice grown by molecular-beam epitaxy (MBE). At low temperatures, the field-dependent Hall data indicate the presence of low-mobility carriers in addition to the high-mobility holes reported previously. Intrinsic electrons become evident at temperatures as low as 50 K. The temperature dependence of the intrinsic carrier density yields information concerning the band gap and the product of the electron and hole density-of-states effective masses. Photo-Hall measurements were also performed using high-intensity irradiation from a CO₂ laser to generate excess electrons and holes. From these measurements, we obtain the first determination of minority-carrier mobilities in Hg-based superlattices. At 10 K, the minority electron mobility is found to be slightly lower than that of the majority holes. Free-carrier lifetimes have been studied by three independent techniques: photo-Hall analysis, transient-decay measurements, and photoconductive response. The lifetime is found to be on the order of 1 ns.