Interface Effects on the Spectral Response of Liquid Phase Epitaxial n-GaAs Radiation Detectors

Two undesirable features exhibited by gold surface barrier detectors from liquid phase epitaxial (LPE) n-GaAs are the variation in pulse height response with bias and multi-peaking effects near full depletion. Capacitative attenuation by the high resistivity epitaxy-substrate interface (ESI) layer is considered to be the origin of these effects. Such anomalous interface layers are well known in the application of LPE GaAs to Gunn oscillator devices and a review of their properties is presented. The response of detectors at room temperature when subjected to IR illumination was markedly improved in the multi-peaking region and slow components in the pulse rise time were removed. The presence of a deep level acceptor in the ESI layer 0.31 - 0.76 eV from the valence band is inferred. Other methods for the reduction of ESI effects are discussed.