High efficiency photodetectors based on high quality epitaxial germanium grown on silicon substrates

We demonstrate Ge/Si heterojunction photodetectors based on high quality epitaxial germanium grown on silicon. Germanium deposited by ultra-high-vacuum chemical vapor deposition (UHV-CVD) undergoes thermal annealing cycles which reduce the number of dislocations and, thus, improve the overall quality. The photodetectors exhibit record responsivity of 0.55 A/W and a sub-ns photoresponse at 1.3 μm. We describe the fabrication process as well as a complete optoelectronic characterization of the devices.