Effect of substrate miscut on low-temperature homoepitaxial growth on Si(111) mediated by overlayers of Au: Evidence of step flow

Abstract

Observations of homoepitaxialgrowth on low-angle miscut (∼0.1°) Si(111) substrates through an overlayer of Au, together with earlier results on highly miscut Si(111) surfaces, indicate that growth in this system occurs by step flow. The growth temperatures were between 375 and 500 °C. In the optimum range of Au coverage (0.6–1.0 ML), ion channeling measurements yield at best χmin=5.0%, and cross-sectional transmission electron microscopy reveals stacking faults on (111) planes. Films produced under similar conditions on bare Si(111) substrates are much more defective. On the other hand, the defect density in the present films is higher than that in filmsgrown on substrates with a higher miscut angle. The improvement in film quality resulting from the Au overlayers is attributed to an increase in the diffusion length of the Si adatoms, caused by Aupassivation of the Si terraces. It is suggested that Au is more efficient than other overlayers in promoting step flow because Au passivates the Si(111) terraces without passivating the step edges.