Radiation sustenance of HfO_2/β-Ga_2O_3 metal-oxide-semiconductor capacitors: gamma irradiation study

摘要

beta-Ga2O3 is an interesting new generation wide bandgap semiconductor for power device applications. The gamma irradiation was performed on the HfO2/beta-Ga2O3-based metal-oxide-semiconductor capacitors at 1 kGy and 200 kGy doses. The leakage current density variation at -1 V is 3.47 x 10(-7) A cm(-2), 5.90 x 10(-7) A cm(-2) and 4.91 x 10(-6) A cm(-2) for the pristine, 1 kGy and 200 kGy devices, respectively. In the case of substrate injection, the Schottky emission mechanism appears to be dominant in the 0.65 to 2.0 MV cm(-1) electric field range. The barrier heights (Ni/HfO2/beta-Ga2O3) 0.95 eV, 0.86 eV and 0.83 eV were extracted from Schottky emission for the pristine, 1 kGy and 200 kGy doses, respectively. However, as the dose increases to 200 kGy, the charge-trapping favors the trap-assisted Poole-Frenkel (PF) tunneling mechanism. In this case, the PF emission mechanism seems to be dominant for the pristine and 1 kGy in the range of 2.0-4.0 MV cm(-1), whereas for 200 kGy it is 1.45 to 4.0 MV cm(-1) which indicates that the defect assisted PF tunneling is predominant at 200 kGy irradiation dose. There is an increase in the density of oxide traps (D-ot) changes from 1.14 x 10(12) cm(-2) eV(-1) to 1.47 x 10(12) cm(-2) eV(-1), and the density of interface traps has increased from 1.95 x 10(11) cm(-2) eV(-1) to 3.80 x 10(11) cm(-2) eV(-1) for the pristine and 200 kGy samples, respectively. The peaks of Photoluminescence show that the three bands of defects centered at 3.0, 2.7 and 2.2 eV. These peaks have possibly arisen from the vacancies of oxygen. At 200 kGy high dose, the defect band emissions were found at 2.9, 2.6 eV and a broad emission at 2.1 eV indicates the increase in the denisty of oxide-trapped charges within the HfO2 layer.