Doping of high concentration of Beryllium in GaAs layers, by molecular-beam epitaxy

Doping processes of high concentrations of Be in GaAs layers by molecular-beam epitaxy (MBE) at low temperatures with different growth rates were investigated in order to explore the possibility of the low-temperature MBE growth for obtaining highly non-equilibrium structures. A high concentration of acceptor Be atoms with a hole concentration of 5.65 x 1020 cm-3 were obtained with a substrate temperature 300 oC and a low growth rate 0.03 μm/h, while an increase in either the substrate temperature or the growth rate resulted in lower hole concentrations. These results suggest unique properties of the low-temperature MBE growth; long-distance diffusions of solute atoms are inhibited at a low growth temperature, while a low growth rate gives surface or near-surface atoms a sufficient time to form a low-energy configuration at a low growth temperature.