Floating-base germanium-tin heterojunction phototransistor for high-efficiency photodetection in short-wave infrared range

• DOI: 10.1364/oe.25.018502
• Publication Date: 2017-07-24T17:35:41Z
• Authors: Wei Wang; Yuan Dong; Shuh-Ying Lee; Wan-Khai Loke; Dian Lei; Soon-Fatt Yoon; Gengchiau Liang; Xiao Gong; Yee-Chia Yeo
• Keywords: 0103 physical sciences; 01 natural sciences; 7. Clean energy

The floating-base germanium-tin (Ge1-xSnx) heterojunction phototransistor (HPT) is designed and investigated as an efficient optical receiver in the short-wave infrared range. Simulations indicate that as the Sn content increases, the responsivity significantly increases due to a higher absorption coefficient and a larger valence band offset between Ge and Ge1-xSnx. Ge0.935Sn0.065 HPTs that incorporated high-quality Ge0.935Sn0.065 film grown by molecular beam epitaxy were fabricated, demonstrating optical response beyond wavelength of 2003 nm. At a low bias voltage of 1.0 V, optical response enhancement of ~10 times was achieved over the conventional Ge0.935Sn0.065 p-i-n photodiode. High responsivities of ~1.8 A/W at 1550 nm and ~0.043 A/W at 2003 nm were demonstrated with low dark current density of 0.147 A/cm2.