The growth and carrier transport properties of sputter deposited GaAs thin films doped with silicon and magnesium

Thin films of GaAs were deposited with a triode sputtering system onto single crystal GaAs semiinslating substrates. Most of the films were doped by the cosputtering of Si for n type or Mg for p type films. The electrical resistivity and Hall Effect were measured by the van der Pauw technique to obtain the carrier concentration and mobility as a function of temperature. Analysis of these data determined that the dopant energy levels had created a band which merged with the production band. The characteristics of this merged band structure controlled the free carrier concentration. It was determined that the dopant density was controlled by the duty cycle of the bias voltage on the dopant target. The resistivity of the n type films at room temperature ranged from 0.036 Ohm cm to 20.8k Ohm cm. The most important mobility limitations were found to be ionized impurity scattering from the high doping densities and grain boundary scattering from the film disorder. The average grain size was determined from grain boundary scattering analysis to be about 50 to 100 A.