Growth of In xGa 1− xAs on GaAs (001) by molecular beam epitaxy

Abstract

As a precursor to investigating the growth of In x Ga 1− x As on Si, a series of 2.8 ± 0.2 μ m thick films of various compositions ( x = 0, 0.13, 0.56 and 1.0) have been deposited by molecular beam epitaxy onto (001) GaAs on-axis substrates, using a minimized As 4 flux and a range of growth temperatures. In addition, a series of layers were grown at a fixed temperature of 350°C over the whole composition range. It was found that the electrical and structural characteristics of InAs and In 0.56Ga 0.44As were very similar, in both cases the layers were n-type, and growth below 330° produced a rapid deterioration of crystalline quality with the associated dislocations/defects being electrically active. In addition, the characteristics of GaAs and In 0.13Ga 0.87As were also found to be very similar. Both were doped with Si to make them conduct and showed a transition to insulating behaviour on reducing the growth temperature below ∼ 480±10°C; above this temperature good mobilities were obtained. Increasing the growth temperature for all the In containing alloys produced a gradual increase in surface roughness up to the point at which In accumulation on the surface occurred (∼410°C for InAs, ∼510°C for In 0.56Ga 0.44As and ∼550°C for In 0.13Ga 0.87As). Growth at 350°C showed a rapid deterioration in crystalline quality as x approached 0.5, as can be illustrated by a pronounced maximum in the X-ray diffraction peak width.