Experimental Studies on Electronic Properties of HgTe/CdTe and Hg(1-x)Cd(x)Te/CdTe Heterostructures and Superlattices

摘要

In this project the electronic properties of superlattices made of alternating layers of mercury telluride and cadmium telluride have been studied at low temperatures T (down to 0.5 K) and in high dc magnetic fields (up to 29 T.) There were two motivations for performing these studies. 1) Whereas superlattices made from III-V materials such as Aluminum Gallium Arsenides and Indium Phosphide have been fabricated and shown to support very high mobility electrons in two-dimensional wells, similar studies had not been performed on the II-VI compounds. In 1982, Dr. Jeff Cheung at Rockwell, Thousand Oaks, succeeded in fabricating superlattices of HgTe and CdTE using a novel laser flash evaporation technique. initial studies by our group (then at University of Southern California) showed that prospects looked good for realizing excellent two-dimensional electronic devices despite the poor mobility of the early samples. 2) On the practical side, far-infrared (FIR) detectors made from the bulk alloy Hg(1-X)Cd(X)Te suffer from inhomogeneity problems which lead to spatial variations of the gap, especially in the 10 micrometer range. Following suggestions by McGill and Schulman (that the gap superlattice HgTe-CdTe can be tuned by changing the periodicity) we also explored the FIR capabilities in the Rockwell samples. We made very extensive studies of the weak localisation effects could be observed in the weak field magnetoresistance in fields under 40 Gauss. By fitting the data to the theory of Hikami et al we extracted quite convincing numbers for the spin-orbit scattering rate and the inelastic scattering rate.