Electrical properties and structural defects of p-type GaN layers grown by halide vapor phase epitaxy

The electrical properties and structural defects of p-type GaN layers with Mg concentrations from 8.0 x 1018 to 8.3 x 1019 cm-3 grown by halide vapor phase epitaxy (HVPE) were investigated. In all samples, p-type conduction was confirmed at room temperature. The hole concentration at room temperature decreased in a heavily Mg-doped sample. By analyzing the results of Hall-effect measurements at various temperatures, the acceptor concentration decreased in a heavily Mg-doped sample, whereas the compensating donor concentration increased. These results affect the decrease in the hole concentration. The hole mobility decreased with increasing acceptor concentration. In the heavily Mg-doped sample, pyramidal inversion domains (PIDs) were formed. The size of each PID in an HVPE-grown sample is in good agreement with that Mg-doped GaN layers grown by metalorganic vapor phase epitaxy (MOVPE). Thus, the formation mechanism of PIDs in HVPE-grown samples is possibly the same as that in MOVPE-grown samples. Energy-dispersive X-ray spectroscopy shows that Mg atoms accumulate in PIDs, which suggests that Mg atoms in PIDs are electrically inactive, inhibiting the increase in the acceptor concentration. These results are useful guidelines for fabricating p-type GaN layers with higher hole concentrations by HVPE.

Automated summary

This study investigated the electrical properties and structural defects of p-type GaN layers with different Mg doping concentrations grown by HVPE. It was found that high Mg doping concentrations lead to a decrease in hole concentration and the formation of pyramidal inversion domains (PIDs). Energy-dispersive X-ray spectroscopy showed that Mg atoms accumulate in PIDs, inhibiting the increase in acceptor concentration.