Analysis of Responsivity and Signal-to-Noise Ratio in PEPT

We analyze the responsivity and signal-to-noise ratio (SNR) of a punchthrough enhanced phototransistor (PEPT). Measurement results show that the PEPT exhibits a good response to light over a wide range of intensity. Beca use the responsivity is still as high as 10 super(6) A/W when the bias voltage is as low as 0.2 V, the device is suitable for ultra-low voltage applications. Meanwhile, with 1-10 mu A bias current, the PEPT shows the best performance for the responsivity and SNR. When incident light is as low as 3.8 x 10 super(-8) W/cm super(2), the responsivity reaches approximately 10 super(8) A/W. The super high responsivity of PEPTs makes it possible to fa bricate small sized photodetector.