Electrical Properties of p-Ge and p-GeSn materials grown on n-Si substrates

The electrical properties of {\em p\em}-Ge and {\em p\em}-Ge$_{1-y}$Sn$_{y}$ ($y$=0.06-0.1\%) grown on {\em n \em}-Si substrate were investigated through temperature-dependent Hall-effect measurements. It was found that there exists a degenerate parallel conducting layer in Ge$_{1-y}$Sn$_{y}$/Si as well as a second, deeper acceptor in addition to a shallow acceptor. Additionally, a conductivity type conversion from {\em p \em} to {\em n \em} was observed between 370 and 440 K for these samples. The parallel conducting layer dominates the electrical properties of the Ge$_{1-y}$Sn$_{y}$ layer below 50 K, and also significantly affects those properties at higher temperatures. The conductivity type conversion and causes of the degenerate conduction layer will be discussed.