The electric and photoelectric characteristics of Ge-ZnSe heterodiodes

The Ge-ZnSe heterojunction has been prepared by vacuum evaporation of the ZnSe onto single-crystal p-type germanium substrates. The growth conditions have been studied in terms of epitaxial growth on different crystallographic orientations in degrees of vacuum down to the ultra-high-vacuum region. Measurements have also been made of the electrical characteristics, capacitance properties, and photoelectric response of the diode. From these measurements a realistic band model has emerged involving intrinsic and extrinsic defects present in the bulk and interfacial region of the zinc selenide. The results of this investigation are compared with those from devices grown by vapour phase epitaxy and the data presented suggests that a Mott-type barrier rather than a Schottky barrier is present at the germanium-zinc-selenide interface. Techniques have been developed for the removal of this Mott barrier and the resulting change in the physical properties and band structure will be given. Possible applications of heterojunctions with this particular band structure will be discussed.