THE GROWTH AND CARRIER TRANSPORT PROPERTIES OF SPUTTER-DEPOSITED GALLIUM-ARSENIDE THIN FILMS DOPED WITH SILICON AND MAGNESIUM

Thin films of GaAs were deposited with a triode sputtering system onto single crystal GaAs semi-insulating substrates. Most of the films were doped by the co-sputtering 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 conduction 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 electron mobility of the n-type films at room temperature ranged from 81 cm(\u272)/V-s to 261 cm(\u272)/V-s. The average grain size was determined from grain boundary scattering analysis to be about 50 to 100 (ANGSTROM). It is expected that refinements in the deposition process could result in better films with larger grain size and higher mobilities