Scanning Tunneling Microscopy of the GaN(000 ) Surface

In-situ scanning tunneling microscopy studies have been performed on the GaN(000 ) surface. Four dominant reconstructions have been observed: 1×1, 3×3, 6×6, and c(6×12). The 1×1 structure is formed by annealing the as-grown GaN surface to desorb excess Ga atoms. The higher order reconstructions are formed by depositing sub-monolayer quantities of Ga atoms onto this 1×1 surface. STM images showing the details of the reconstructions are presented, and results of quantitative measurements of the number of Ga atoms required to form the various reconstructions are reported. Structural models are compared with the STM data. Reversible order/disorder phase transitions and adatom motion on the GaN surface are discussed.