The Production of Doped Amorphous GaAs by Co-Sputtering With Mo

Stoichiometric amorphous GaAs films with intrinsic properties have beer produced by R.F. Sputtering in pure argon at high substrate temperature of 290°C. The electronic and the optical properties of this material have been modified by the molybdenium co-sputtering. This paper reports: on several modified material parameters including the electrical conductivity, thermal activation energy and optical gap. Atomic Mo concentrations up to 1.24% have been investigated. It is observed that the room temperature conductivity can be controlled over about six orders of magnitude, which corresponds to a shift in the Fermi level of 0.45 eV towards the conduction band edge. For optical parameters, the optical gap has been reduced by 0.1 eV. An additional absorption tail due to localized states introduced by doping atoms is observed. It is concluded that our a-GaAs have the main requirement, i. e low density of defect gap states, for effective doping with analogy to a-Si prepared either by glow discharge or by sputtering in argon-hydrogen plasma.