Electron irradiation induced defects and schottky diode characteristics for metalorganic vapor phase epitaxy and molecular beam epitaxial n-GaAs

Abstract

A considerable body of information is available in the literature concerning the effects of high energy electron irradiation on the formation of deep trapping levels in GaAs. Most of these studies have dealt with bulk material or material grown by vapor phase epitaxy (VPE). However, whether these studies are representative of GaAs epilayers grown by metalorganic vapor phase epitaxy (MOVPE) or molecular beam epitaxy is not clear, particularly when the gallium and arsenic species used in the growth and hence optimal conditions for growth, differ widely between techniques. In fact, the results reported in this study show significant differences in the behavior of material produced by these techniques. Deep level transient spectroscopy (DLTS) is used in this work to characterize the deep electron traps formed during 7 MeV electron irradiation. In addition, the current voltage characteristics of the Schottky diodes used in the DLTS studies have been evaluated before and after irradiation to ascertain the effects of irradiation on device performance. It has been found that an additional trapping level is produced in MOVPE-grown material of high background doping and that the carrier removal in this material is not a simple function related to increased electron fluence as observed in previous studies on VPE material.