STRUCTURAL-ANALYSIS OF EPITAXIAL GAAS ON ON-AXIS (100) SI GROWN BY IONIZED SOURCE BEAM EPITAXY

In order to understand the effects of ionized source beam epitaxy (ISBE) on defect formation and film growth kinetics, GaAs films grown on on-axis (100) Si with an ionized As source beam were compared with those grown with conventional neutral source beams using results from reflection high-energy electron diffraction and cross-section transmission electron microscopy (XTEM) analysis. Compared to the very irregular surfaces of the films grown with neutral source beams, very flat surfaces, and higher crystal quality of the films were obtained by the As beam ionization and acceleration. The results of defect characterization using XTEM showed that no antiphase domains were present in the ISBE-grown GaAs epilayer and that the nature of the dislocations and stacking faults in the GaAs epilayer was quite different as compared to the neutral source beam case. This evidence strongly suggests that ionization and acceleration of the As source beam not only enhances the As adatom mobility, but also stimulates the Ga adatom migration so as to prevent Ga atoms from aggregating to form three-dimensional islands during the early stages of the film growth. As a result, the enhanced As and Ga mobilities obtained with the ISBE process promote the coalescence process, thus transforming the nucleation dynamics from three-dimensional growth to layer-by-layer growth.