Observation of a (√3 x √3)-R30° reconstruction on GaN(0001) by RHEED and LEED

摘要

A new reconstruction of √3 x √3-R30° has been observed on a GaN film grown on a 6H-SiC (0001)-√3 x √3 surface using RHEED and LEED experimental techniques. The experimental LEED PF shows that the GaN film is Ga-terminated hexagonal. The surface is a mixture of two structures with a single bilayer height difference between them. One is a √3 x √3-R30° reconstruction with Ga-adatoms occupying the T4 sites. Another is a Ga-terminated 1 x 1 with no extra Ga on top. The area ratio of the √3 x √3 part to the 1 x 1 part is slightly larger than 1. The first principle total energy calculations and Tensor-LEED Ⅰ-Ⅴ curves simulations further confirm this structure model.