The fabrication of both n-type and p-type GaAs thin films deposited by troide sputtering

Abstract

Thin films of GaAs were deposited with a triode sputtering system onto single-crystal GaAs semi-insulating substrates. The films were doped to various densities by co-sputtering a silicon or magnesium target with an adjustable duty cycle. The electrical resistivity and Hall effect were measured by the Van der Pauw technique to obtain the carrier concentration and mobility as functions of temperature. 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 films at room temperature ranged from 0.036 to 20.8 × 10 3 ohmcm. The variation of the carrier concentration as a function of temperature was found to be well described by a merged conduction-dopant band model. The electron mobility of the n-type films at room temperature ranged from 81 to 261 cm 2 V −1 s −1. The most important mobility limitations were found to be grain boundary scattering in all films and ionized impurity scattering in the most highly doped films. The average grain size was found from the grain boundary scattering analysis to be about 50–100 Å and this size was confirmed by reflection electron diffraction and electron-beam-induced current analysis.