GeSn p-n-p Heterophototransistor on Si

This work focuses on the growth of GeSn p-n-p hetero bipolar phototransistors (HPT) with a Sn content of 6% and a Ge reference bipolar phototransistor. The devices were grown on Ge virtual substrates on Si using molecular beam epitaxy. The transistors were created as two-terminal devices with a free-floating base. Based on the electro-optical analysis, it is evident that the GeSn HPT performs much more effectively in inverse operation compared to regular operating mode. This seems to be attributed to the band offsets. The GeSn HPT's photoresponse does not show a linear correlation with the incident optical power. It has been discovered that the power law factor is less than one, resulting in a noticeably greater amplification of the photocurrent at low optical powers. At a wavelength of 1550 nm and an optical power of 0 dBm, our fabricated GeSn HPT achieves an optical responsivity of 1.5 A/W, which is significantly higher than most of the previously reported values. These findings pave the way for further advancements in high-performance GeSn HPT for optical communication applications.