The role of defects on CdTe detector performance

We present results from a characterisation of bulk defects in CdTe wafers, and their role in the degradation of charge transport performance of CdTe radiation detectors. Sub-bandgap IR microscopy and X-ray Lang topography have been used to characterise material quality prior to device processing. IR microscopy clearly identifies extended defects such as tellurium precipitates in the material bulk, whilst Lang topography characterises stacking faults, crystallite boundaries and other crystallographic features in the near-surface region. After fabrication of contacts onto the material, ion beam induced charge imaging is used to investigate the correlations between material defects and charge transport. Digital ion beam induced charge imaging is used to produce high resolution maps of charge signal amplitude, carrier drift time, and carrier drift mobility.