Effect of temperature on the mutual diffusion of Ge/GaAs and GaAs/Ge

We studied the diffusion of Ge, As and Ga in GaAs/Ge and Ge/GaAs epilayers grown at different temperatures by metal-organic vapor phase epitaxy using iso-butylgermane, arsine and trimethylgallium in hydrogen atmosphere at low pressure. The use of low temperature buffer layers was investigated in order to overcome the diffusion problem. High-resolution X-ray diffraction and transmission electron microscopy were used to assess the crystal quality, while secondary neutral mass spectrometry has been employed to investigate diffusion profiles in the samples. As it is well known, the diffusivity of the atoms (e.g. Ga, As, Ge) and intermixing of layers during sample preparation strongly depend on the substrate temperature. We found that the use of a low temperature GaAs buffer layer reduced the diffusion in GaAs/Ge epitaxy at 600 °C; while a Ge low temperature buffer layer was not effective in reducing the interdiffusion in Ge/GaAs epitaxy at 700 °C.