Transient Photoconductive Gain in A-Si : H Devices and Its Applications in Radiation Detection


Using the transient behavior of the photoconductive-gain mechanism, a signal gain in radiation detection with a-Si : H devices may be possible. The photoconductive gain mechanism in two types of hydrogenated amorphous silicon devices, p-i-n and n-i-n configurations, was investigated in connection with applications to radiation detection. Photoconductive gain was measured in two time scales: one for short pulses of visible light ( < 1 µs) which simulate the transit of energetic charged particles or γ-rays, and the other for rather long pulses of light (≥ 1 ms) which simulate X-ray exposure in medical imaging. The photoconductive gain in our devices could be calculated by comparing the photo-induced signals from n-i-n photoconductors and forward biased p-i-n photodiodes to the maximum signals from corresponding reverse biased p-i-n photodiodes. We used two definitions of photoconductive gain: current gain and charge gain which is an integration of the current gain. We obtained typical charge gains of 3-9 for short pulses and a few hundreds for long pulses at a dark current density level of 10 mA/cm². Various gain results are discussed in terms of the device structure, applied bias and dark-current density.


Mining and Nuclear Engineering

Keywords and Phrases

A-Si : H; N-I-N Photoconductor; P-I-N Photodiode; Photoconductive Gain; Photoconductivity; Photocurrent

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Article - Journal

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