Amorphous silicon phototransistor on a glass substrate

An amorphous silicon n⁺-i-p⁺-i-n⁺thin-film phototransistor was made on a glass substrate. The p⁺base is very thin (∼ 200 Å) compared with 2000 to 5000 Å of the collector i-layer. Therefore, the emitter current which is induced from the photogenerated flux in the collector i-layer is very high. In addition, hole lifetime (minority carrier in the emitter) and transit time are very short, the device possesses fast rise time and fall time of 30 µs, which is mainly governed by the junction capacitance-resistance charging effect and strays.