Reverse-annealing phenomenon during the high-temperature implantation of Ar+ into GaN

A systematic investigation of the damage accumulation in GaN films induced by 150keV Ar ions as a function of implantation temperature and dose rate has been conducted. The depth distribution of the disorder in the Ga sublattice has been measured by RBS/channeling spectrometry with a glancing angle detector geometry to provide enhanced depth resolution. Two disordered regions were identified in the damage depth distribution: a near-surface peak and a bulk damage peak. These regions exhibit different behavior as a function of implantation temperature. The height of the near-surface peak, as expected, decreased with implantation temperature approaching the magnitude of the unimplanted sample. The displaced atomic density in the bulk damage peak also followed this tendency and decreased in the temperature range from room temperature to 500degreesC. The implantation at higher temperatures resulted in an increase in the amount of damage, reaching a maximum at about 700degreesC and displayed a characteristic "reverse annealing" behavior. Further increase of the implantation temperature to 1000degreesC reduced the disorder. The influence of the dose rate and implantation temperature on the radiation damage accumulation is discussed.