Sensitive depth of semiconductor radiation detectors in current and pulse mode operations (abstract)

Abstract

The sensitive depth of semiconductor radiation detectors is widely believed to be the depletion depth. Recent experiments, however, showed that the x-ray response of surface-barrier detectors is independent of the depletion depth when operated in dc current mode [K. W. Wenzel and R. D. Petrasso, Rev. Sci. Instrum. 59, 1380 (1988)]. We report experimental observation of such detectors in both current mode and pulse mode operations to alpha particles and to short-pulsed x rays (0.1–1 μs). It demonstrates that the difference in sensitivity between the detector’s dc response and pulsed-signal response is caused by the different charge collection time in depleted and undepleted regions. Therefore, the sensitive depth depends on how the detector is operated, and is not always the depletion depth. The construction and operation of the short-pulsed x-ray source is also described. This work was supported by the U.S. Department of Energy contract No. DE-AC02-78ET51013.