Chemical Sputtering Yield as a Function of Ion Incident Angle in Wurtzite-Type GaN Crystal

A molecular dynamics simulation has been carried out to investigate the sputtering yield of wurtzite-type GaN (0001) surface with Cl-adsorbed layer. Sputtering yields of Ga and N are 0.3-0.4 and 0.1-0.15 at the incident Ar energy of 250 eV, respectively. The sputtering yield shows only a weak dependence on ion incident angle for the range of 60 to 90 degrees, whereas the yield increases as the ion incidence is more inclined for GaN surface without Cl-adsorbed layer. Ga is sputtered in the form of Ga-Cl$_{2}$, and sometimes in the form of Ga-Cl, Ga-Cl$_{3}$, and Ga$_{x}$N$_{y}$Cl$_{z}$. These products escape from the surface in the time range mainly of 200-500 fs after the impact of incident Ar ion. There are small amount of products escaping in the time range of 500-5000 fs. Single N atom is physically sputtered within 100 fs after the Ar incidence, whereas Ga is not singly sputtered.