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. Because the responsivity is still as high as 10⁶ 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 μA bias current, the PEPT shows the best performance for the responsivity and SNR. When incident light is as low as 3.8×10^?8 W/cm², the responsivity reaches approximately 10⁸ A/W. The super high responsivity of PEPTs makes it possible to fabricate small sized photodetector.