Temperature dependent biaxial texture evolution in Ge films under oblique angle vapor deposition

The morphology and texture of Ge films grown under oblique angle vapor deposition on native oxide covered Si(001) substrates at temperatures ranging from 230 °C to 400 °C were studied using scanning electron microscopy, X-ray diffraction and X-ray pole figure techniques. A transition from polycrystalline to {001}<110> biaxial texture was observed within this temperature range. The Ge films grown at substrate temperatures < 375 °C were polycrystalline. At substrate temperatures of 375 °C and 400 °C, a mixture of polycrystalline and biaxial texture was observed. The 230 °C sample consisted of isolated nanorods, while all other films were continuous. The observed biaxial texture is proposed to be a result of the loss of the interface oxide layer, resulting in epitaxial deposition of Ge on the Si and a texture following that of the Si(001) substrates used. The rate of oxide loss was found to increase under oblique angle vapor deposition.