dc and ac transport in molecular-beam-epitaxy-grown metal/ZnSe/GaAs heterojunction structures

Abstract

The room-temperature electrical transport properties of ZnSe epilayers grown above the critical layer thickness on n+-GaAs substrates by molecular-beam epitaxy have been studied. dc current versus voltage and small-signal ac admittance versus voltage and frequency measurements were made on Schottky contacts (Au or Hg). A novel method of analysis is presented which, extending a previous model to include the three-dimensional effects of current spreading as a function of frequency, allows the ZnSe epilayer resistivity to be obtained. Combining this with the doping concentration obtained from analysis of the C-V characteristics, the ZnSe mobility may be calculated. Mobilities thus measured compare well with our own and other workers’ published Hall mobility data on similar samples, as well as with theoretical calculations. We believe that our results represent a unique and detailed characterization of an epilayer heterostructure on a highly conducting substrate.