Ballistic electron emission microscopy studies of ZnSe–BeTe heterojunctions

Abstract

Ballistic electron and hole emission microscopies, have been used to probe Au/ZnSe/GaAs and Au/ZnSe/BeTe/GaAs (001) heterostructures as a function of the ZnSe/BeTe interface stoichiometry. Ballistic electron and hole transport into n- and p-type ZnSe epilayers, respectively, were observed with spectra that conformed well to theoretical behavior. The measured average voltage thresholds +1.25 (p type) and −1.41 V (n type) were in good agreement with previously observed values for the Au/ZnSe Schottky barrier heights and consistent with the value of the ZnSe direct band gap (2.67 eV). However, the ballistic transport into the BeTe conduction bands required to measure the ZnSe/BeTe conduction band offset was not confirmed. Time-dependent and spatial variations of the voltage thresholds were observed for p- and n-type diodes, with and without BeTe epilayers, and were presumed to be linked to switching Fermi level pinning positions from varying Au/ZnSe interface states densities.