Study of radiation damages accumulation and crystalline lattice recovery in gallium nitride implanted with argon(+) ions.

摘要

A systematic investigation of damage accumulation and crystalline lattice recovery in GaN films implanted with Ar+ ions has been conducted. Depth distributions of disorder and implanted species were studied by RBS/Channeling and SIMS, respectively. The structure of the defects was investigated by TEM. Damage accumulation was measured as a function of implantation temperature, dose and dose rate. Two disordered regions were identified in the damage depth distribution: a surface peak and a bulk damage peak. Both damage peaks exhibited a well-defined transition dose (3 × 10 15 cm−2) above which the damage level increased dramatically. With increasing implantation temperature up to 1000°C, the amount of damage in the surface peak decreased for the whole dose range studied. With the exception of a narrow dose interval between 8 × 1014 and 4 × 1015 cm−2, the disorder in the bulk damage peak also decreased with the increase of temperature. In this narrow dose interval the amount of disorder decreased in the temperature range from RT to 500°C. The implantation at higher temperatures resulted in an increase in the amount of damage, reaching a maximum at about 700°C and displayed a characteristic “reverse annealing” behavior. Further increase of the implantation temperature to 1000°C reduced the disorder. TEM observations showed that the reverse annealing is due to the formation of carbon nitride precipitates in the implanted layer.; Damage recovery of GaN implanted at various temperatures was studied as a function of annealing time and temperature. The implantation temperatures were chosen in such a way that the radiation damage accumulation mode was both within the reverse annealing (T_imp = 600°C) and outside it (T_imp = RT and 300°C). The isothermal annealing results demonstrated that fast lattice recovery took place in the first 2 s and almost terminated in 20 s. The damage recovery was better for the samples annealed at RT comparing to implantations at the elevated temperatures. In the samples implanted at 300°C long stacking faults were formed which persisted to anneal temperatures up to 900°C. The data indicated that the anneal characteristics of the lattice disorder are influenced by the type of defects formed during the implantation, which are in turn determined by the implantation conditions.