Method and apparatus for interrupted transit time transient photoconductivity measurements

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Abstract
The authors describe a simple and economic but versatile time-of-flight (TOF) transient photoconductivity apparatus which enables RC transient-free interrupted transit time (ITT), as well as delayed and advanced photoexcitation mode measurements, to be carried out on high resistivity solids. The apparatus uses a short (130 ns) intense light pulse from a xenon flash bulb for photogeneration and high voltage complementary HEXFETS to apply the bias voltage. The ITT method was applied to examine charge trapping kinetics in vacuum-deposited amorphous Se layers suitable for X-ray medical imaging. It is shown that the ITT technique was successful in identifying two species of traps and extracting the hole trapping and release times, which are much longer than the transit times, even when the conventional TOF signal showed very little evidence of trapping.