Growth of high-quality epitaxial GaAs films by sputter deposition

Abstract

Epitaxial GaAs films have been grown on (100) Cr-doped GaAs substrates by sputter deposition from an undoped GaAs target. Unintentionally doped samples were high resistivity (105–106 Ω cm) n type with room temperature mobilities as high as 5000 cm2/V sec. Residual oxygen and carbon contamination was minimized through the use of a liquid-nitrogen-cooled shroud surrounding the discharge during deposition. Excess arsenic was provided to the growing film from an effusion cell. Film doping was accomplished using either an evaporated source (Mn) or the addition of a gas-phase impurity (H2S) during sputter deposition. Mn-doped p-type films were grown with room-temperature carrier concentrations between 1.3×1017 and 2.5×1018 cm−3 and corresponding hole mobilities of 240–95 cm2/V sec. The S-doped films were n-type with S concentrations, as determined by secondary-ion mass spectrometer (SIMS), up to the solid solubility limit and sharp doping profiles with widths of ∼200 Å. In all cases the dopant incorporation probability was controllable by varying the negative bias on the growing film.