GaP/Si heteroepitaxy by complex ion beam sputtering

Abstract

We have investigated the sputter deposition using a complex ion beam formed with the mixture of Xe and PH3 to grow GaP epitaxial films on Si substrates. The complex ion beam was formed by the cold cathode ion source into which Xe and PH3 gases were fed via variable-leak valves. To reduce the ion beam irradiation damage in the deposited film, the Si substrate was arranged in parallel to the polycrystalline GaP target which was sputtered by the oblique irradiation of the ion beam. The ion beam acceleration voltage was kept at 6.5 kV and the ion beam current density was about 100 μA/cm2 on the GaP target. The GaP films were deposited at a chamber pressure of 2×10−5 Torr, and the substrate temperature was selected between 400 and 600 °C. The crystalline quality of the deposited GaP films was examined by the reflection high-energy electron diffraction and the surface morphology was observed by the scanning electron microscope. Single-crystalline GaP films were not obtained by the Ar+ or Xe+ ion beam sputter deposition, but were obtained by the complex ion beam sputter deposition using the gas mixture of Xe:PH3 =1:1 as a source gas at a substrate temperature of 500 °C, and also by the PH3 ion beam sputter deposition. The surface morphologies of the GaP films grown by the complex ion beam sputtering were smoother compared with those films deposited by the Ar+ or Xe+ ion beam sputtering.