Protective Surface Coatings on Semiconductor Nuclear Radiation Detectors

Surface states on germanium p-i-n junctions have been investigated using deep level transient spectroscopy (DLTS) and collimated beams of 60 keV gamma-rays. The DLTS spectra have a characteristic signature for each surface treatment but the spectra are complex and not readily interpretable as to suitability for radiation detectors. Collimated gamma-ray beams give a direct measure of surface channel effects and typeness. Hydrogenated amorphous germanium (a-Ge:H) was explored as a surface layer to adjust the electrical state and passivate the surface. Our measurements show that these layers produce flat band conditions, introduce no additional noise and appear to be stable against a variety of ambients.