Electrical and optical properties improvement of GeSn layers formed at high temperature under well-controlled Sn migration

Electrical and optical properties of GeSn layers formed at various growth conditions under changing deposition temperature (Td) and deposition speed (vd) were systematically investigated. A high Sn content of 3.0% leads to high electron mobility and electron concentration for an as-deposited sample compared with the Sn content of 1.9%. Subsequent annealing at 550 °C after the growth is effective for improving the mobility and the activated carrier concentration. Moreover, the high vd and Td growth makes it possible to get clear photoluminescence (PL) signal from the band-to-band transition of the GeSn layers. The annealing at 550 °C leads to the high and sharp PL spectra compared with those for the as-deposited samples. Consequently, we found that the high vd and Td growth of the GeSn layers suppressing the Sn migration is quite important for getting electrical and optical properties to realize future electrical and optical devices.