Investigation of gap states near conduction band edge in vicinity of interface between Mg-ion-implanted GaN and Al₂O₃ deposited after ultra-high-pressure annealing

The gap states near the conduction band edge (E (C)) in the vicinity of the interface between Mg-ion-implanted GaN and Al2O3 deposited after post-implantation annealing were investigated in the range between E (C )- 0.15 eV and E (C )- 0.45 eV. For this purpose, capacitance-voltage measurements were performed on MOS diodes with the n-type conduction of Mg-implanted GaN maintained by suppressing the dose. Although the gap state density D (T) was reduced for the sample prepared with the dose of 1.5 x 10(12) cm(-2) by conventional rapid thermal annealing (RTA) at 1250 & DEG;C for 1 min using an AlN protective cap layer, further improvement was achieved by capless ultra-high-pressure annealing (UHPA) at the same temperature for the same duration. Furthermore, the D (T) distributions for the samples with capless UHPA at 1400 & DEG;C for 5 min are comparable to that for the sample with conventional RTA at 1250 & DEG;C for 1 min using the cap layer.