Some properties of CdS/p-Ge heterojunctions grown by chemical transport

Abstract

Some physical properties of CdS/p-Ge heterojunctions made by chemical vapour deposition of single crystal CdS epitaxial layers on (111)p-type nearly degenerate Ge substrates are reported. the equilibrium energy band diagram is discussed in the light of junction capacitance measurements as a function of frequency and of the reverse bias. The presence of interface states in the CdS band gap, with a density maximum at 1.1 eV below the equilibrium Fermi level has been shown. A model for the acceptor nature of the electronic states of misfit dislocations in CdS is suggested. The temperature dependence of theI-V characteristics has been measured in the temperature range 77–300 K. Models for the current flow in both direct and reverse bias conditions are discussed, taking into account the tunneling-recombination or generation-tunneling mechanisms throúgh interface states.