Characterization of a Ge_1-x-ySi_ySn_x/Ge_1-xSn_x multiple quantum well structure grown by sputtering epitaxy

A high-quality Ge_0.88Si_0.08Sn_0.04/Ge_0.94Sn_0.06 multiple quantum well (MQW) structure was grown on a Ge (001) substrate by sputtering epitaxy. The MQW structure was characterized by high-resolution x-ray diffraction and transmission electron microscopy. Surface-illuminated Ge_0.88Si_0.08Sn_0.04/Ge_0.94Sn_0.06 MQW pin photodetectors were fabricated with cutoff wavelengths of up to 2140 nm. The analysis of transitions from spectral response was fitted well with the theoretical calculations. Results suggest that sputtering epitaxy is a promising method for preparing high-quality low-dimensional Sn-based group IV materials and that Ge_1-x-ySi_ySn_x/Ge_1-xSn_x MQWs have potential applications in the development of efficient Si-based photonic devices.