Heteroepitaxy of GaAs on a modified CaF2 surface by an extremely low energy electron beam

The effects of the acceleration energy and dose of electrons on the surface modification of CaF2 for growing heteroepitaxial GaAs on CaF2(111) were investigated, focusing especially on the use of a lower energy beam. Electron Hall mobility measurements of GaAs films revealed that the acceleration energy and the dose are not independent parameters and that there is a specific value of the product of these two parameters (V(E)XD(E)) with which good electrical properties of GaAs films are obtained. Transmission electron microscopy and energy-dispersive X-ray spectroscopy observations showed that excess exposure of the CaF2 surface to the electron beam caused an increase in the dislocation density and Ca contamination in the overgrown GaAs films. The low acceleration energy (around 40 eV) is more desirable, because a wide range of electron doses leads to good GaAs films.