Small-Signal Compact Circuit Modeling of Group IV Material-Based Heterojunction Phototransistors for Optoelectronic Receivers

This paper presents an optoelectronics-based compact equivalent circuit model of an n-Ge/p-Ge
_1-x
Sn
_x
/n-Ge
_1-x
Sn
_x
heterojunction phototransistor (HPT). This paper includes the static electrical and optical characteristics of the device, Gummel characteristics, effect of temperature, and overall noise analysis of HPT based on various parametric variations. We then investigate the effect of parasitic capacitance on the noise performance of the HPT. The estimated results show that the signal-to-noise ratio (SNR) is strongly dependent on not only the operating frequency but also the operating temperature and applied base-bias voltage. Estimated performance shows that SNR of HPT >90 dB up to 100 GHz and >80 dB up to 50 °C can be achieved, which ensured the operation of the device as high-speed and low-noise detector.