Ultrasensitive Si phototransistors with a punchthrough base

Si phototransistors with a punchthrough base were fabricated with regular p lanar technology. Optical conversion gains larger than 15 000 were observed . In addition to very high gain, the unique structure of the device also re sulted in a fast transient response as well as low output noise. The measur ed full width at half maximum of the device transient response is 1.6 ns an d a -3 dB bandwidth of 300 MHz. The measured output noises at different cur rents can be well fitted by the relation i(n)((2) over bar)=2qI(C). (C) 200 1 American Institute of Physics.