Current–Voltage Characteristics of GeSn/Ge Heterojunction Diodes Grown by Molecular Beam Epitaxy

Heterojunction diodes of p-GeSn/n-Ge were fabricated by solid-source molecular beam epitaxy on Ge substrates to investigate their electrical properties. Measurements of the current-voltage characteristics and their temperature and composition dependence were performed to extract the diode parameters of reverse saturation current, ideality factor, series resistance, and shunt resistance. The diodes showed good rectifying behavior with low turn-ON voltages in forward bias. The reverse saturation current increased with increasing Sn content and increasing temperature, and the magnitude of the breakdown voltage decreased with increasing temperature. These results suggest that Ge-Sn diodes may be useful for Ge-based circuits and optoelectronics.