Analyses of GaN (0 0 0 1) and (0001¯) surfaces by highly-charged ions

Secondary-ion mass spectroscopic studies for wurtzite GaN (0 0 0 1) and (0001¯) surfaces grown by hydride-vapor phase epitaxy were carried out using highly-charged ions. The secondary ions of impurities adsorbed on the surfaces, such as proton, H2+, and CmHn+ (m = 1-6 and n = 0-13), were preferentially desorbed by the grazing incidence of Arq+ (q = 6-11). A spectrum peak of Ga+ was observed only in the (0 0 0 1) surface, whereas an enhancement of the peak intensity of N+ was observed in the (0001¯) surfaces. The time difference between the two peaks was also observed in the time-of-flight spectra of protons emitted from the (0 0 0 1) and (0001¯) surfaces. It was concluded that these differences were due to the surface polarity of GaN.