Molecular beam deposition of low-resistance polycrystalline GaAs

Heavy doping of polycrystalline GaAs (poly-GaAs) with Be is investigated using low-temperature molecular beam deposition. A polycrystal grain size of 50-180 nm, which is appropriate for microfabrication, is obtained at a deposition temperature of 370-530°C. The resistivity of poly-GaAs decreases rapidly with increasing doping level NF_A, and it becomes in reverse ratio to N_A when N_A >2 x 10²⁰ cm^-3. Low deposition temperature and high As₄ pressure are also found to be effective in reducing resistivity. The minimum resistivity reported to date of 3.3 x 10^-3 Q-cm is achieved for Be-doped poly-GaAs with a grain size of 120 nm. These results show that the present poly-GaAs is very promising for applications to compound semiconductor devices.