Interface properties of n-ZnSe–p-Ge heterojunctions grown by organometallic chemical vapor deposition

Abstract

Aluminum-doped, n-type ZnSe layers ranging in thickness from several thousand Ångstroms to several microns were grown epitaxially on differently oriented p-type Ge substrates by a low temperature, low pressure organometallic chemical vapor deposition process. The surface morphology and photoluminescence spectra reveal differences between the ZnSe films grown on (100)Ge substrates and those grown on (111)Ge substrates. Photoluminescence spectra of the former films show strong band gap luminescence, whereas the latter films are characterized by a reduced band gap luminescence intensity and an enhanced intensity in the self-activated region. The lattice structure of the ZnSe–Ge interface has been studied by high resolution transmission electron microscopy, and the electrical characteristics of the corresponding n-ZnSe–p-Ge heterojunctions have been measured. Heterojunctions formed on (100) oriented substrates show good diode behavior with dark saturation currents of 1×10−11 A/cm2. Heterojunctions formed on (111) substrates are characterized by poor diode behavior with dark saturation currents of the order of 4×10−8 A/cm2. The difference in the electrical transport properties is attributed to the distinctly different defect structure at the ZnSe–Ge heterojunction interface.