Properties of silicon-doped AlxGa1-xAs grown by molecular beam epitaxy

Abstract

The incorporation of silicon in AlxGa1-xAs grown by molecular beam epitaxy was investigated. In Al0.25Ga0.75As and Al0.35Ga0.65As doping levels were proportional to the incident silicon flux for effusion cell temperatures below 1125°C. At 1125°C the electron concentration saturated at about 2×1018 cm-3 and then decreased slightly. For cell temperatures above 1150°C silicon precipitation observable with an optical microscope took place. Silicon incorporation decreased with increasing growth temperature above 650°C with an activation energy of 2.1 eV. Electron mobilities in excess of 1000 cm2V-1 s-1 were obtained for doping levels above 1×1018 cm-3. Donor activation energies were typically between 5 and 20 meV and increased slightly as the silicon flux was increased.