Dopant behavior in heavily doped polycrystalline Ge1-xSnx layers prepared with pulsed laser annealing in water

A low-temperature process for the formation of heavily doped polycrystalline Ge (poly-Ge) layers on insulators is required to realize nextgeneration electronic devices. In this study, we have systematically investigated pulsed laser annealing (PLA) in flowing water for heavily doped amorphous Ge1-xSnx layers (x approximate to 0.02) with various dopants such as B, Al, Ga, In, P, As, and Sb on SiO2. It is found that the dopant density after PLA with a high laser energy is reduced when the oxidized dopant has a lower oxygen chemical potential than H2O. As a result, for the p-type doping of B, Al, Ga, and In, we obtained a high Hall hole density of 5 x 10(19) cm(-3) for PLA with a low energy. Consequently, the Hall hole mobility is limited to as low as 10 cm(2) V-1 s(-1). In contrast, for As and Sb doping, because the density of substitutional dopants does not decrease even after PLA with a high energy, we achieved a high Hall electron density of 6 x 10(19) cm(-3) and a high Hall electron mobility simultaneously. These results indicate that preventing the oxidation of dopant atoms by water is an important factor for achieving heavy doping using PLA in water. (C) 2018 The Japan Society of Applied Physics.