Gas Phase Doping of Arsenic into (100), (110), and (111) Germanium Substrates Using a Metal–Organic Source

The gas phase doping of arsenic (As) into (100), (110), and (111) germanium (Ge) substrates at 500 to 700 °C using a metal–organic vapor phase epitaxy (MOVPE) system with tertiarybutylarsine (TBAs) as the As source was investigated for the n-type source/drain formation of Ge metal–oxide–semiconductor field effect transistors (MOSFETs). The surface concentration of As analyzed by secondary ion mass spectroscopy (SIMS) was approximately 1×1019 cm-3 and the diffusion constant was one order of magnitude smaller than that of As induced by ion implantation at 700 °C. The diffusion constant was linearly dependent on the As concentration, and the activation energy and pre-exponential factor of the As diffusion constant were found to be 1.9 eV and 6.2×10-3 cm2/s, respectively. The electron carrier concentration profiles were also evaluated by spreading resistance profiling (SRP) to confirm dopant activation.