First detection of gamma-ray peaks by an undoped InSb Schottky detector

The compound semiconductor InSb, because of its very small band-gap energy, high density and high atomic number, is suitable for the substrate of X-ray detectors with high-energy resolution and high efficiency. An InSb Schottky detector is fabricated with an undoped InSb wafer and is used in the measurement of 133Ba gamma-rays. Here, the first observation of an escape peak of 81 keV gamma-rays emitted by 133Ba using an InSb detector is reported. The event ratios of the escape and 81 keV gamma-rays were estimated by a Monte Carlo simulation code as a function of depletion layer thickness and were compared with experimental result.