Negative Conductivity Effects and Related Phenomena in Germanium. Part II

This paper is the second part of a two-part review of recent work on current instabilities and related properties of germanium in high electric fields. In this part the transferred carrier mechanism for producing bulk negative differential conductivity (BNDC) in a semiconductor is discussed. Experimental work on instabilities related to three realizations of this effect, in uniaxially compressed n and p-type Ge, and in n-type Ge at low temperatures with field and current in a 〈111〉 direction, is reviewed. Theoretical understanding of these effects, which is largely qualitative at this time, is discussed. In an appendix a list of materials in which BNDC effects have been observed is presented, with some of the relevant properties of these materials.