High-speed short-wave infrared Si-based GeSn MQW phototransistor: an alternative to existing photodetectors

TLDR: In this article, the authors demonstrate high performance vertical GeSn multiple quantum well (MQW) heterojunction phototransistors (HPTs) on Si substrates for short-wave infrared (SWIR) applications.

Abstract: This work demonstrates high-performance vertical GeSn multiple quantum well (MQW) heterojunction phototransistors (HPTs) on Si substrates for short-wave infrared (SWIR) applications. Estimated results show a strong dependence on the number of QWs (N), incident optical power Pin and capture parameter β . Enhanced carrier and gain confinement cause an increase in responsivity of the device with the QWs in the base layer. However, the frequency performance of the device degrades with more QWs due to the increased forward transit time. On the other hand, the 3 dB cut-off frequency fT is the highest for the lower value of β . In addition, the detectivity and responsivity of the device decrease with an increase in incident optical power due to the change in base potential. The calculated results show that the 3 dB cut-off fT and maximum operating frequency fmax are 18{\text{ GHz}}$?> >18 GHz and 0.147{\text{ THz}}$?> >0.147 THz , respectively for N = 1 at 300 K. The detectivity and noise equivalent power are ∼109cmHz1/2/W and <10−12WHz−1/2 , respectively for N = 3 at 300 K under 0.4 applied bias voltage. These promising results of the presented GeSn MQW HPT can pave the way for efficient low-noise high-speed photodetection applications under a low applied bias voltage.