Investigation of temperature dependent threshold voltage variation of Gd₂O₃/AlGaN/GaN metal-oxide-semiconductor heterostructure

Temperature dependent threshold voltage (V_th) variation of GaN/AlGaN/Gd₂O₃/Ni-Au structure is investigated by capacitance-voltage measurement with temperature varying from 25°C to 150°C. The V_th of the Schottky device without oxide layer is slightly changed with respect to temperature. However, variation of V _th is observed for both as-deposited and annealed device owing to electron capture by the interface traps or bulk traps. The V_th shifts of 0.4V and 3.2V are obtained for as-deposited and annealed device respectively. For annealed device, electron capture process is not only restricted in the interface region but also extended into the crystalline Gd₂O₃ layer through Frenkel-Poole emission and hooping conduction, resulting in a larger V_th shift. The calculated trap density for as-deposited and annealed device is 3.28×10¹¹ ∼1.12×10¹¹ eV^-1 cm^-2 and 1.74×10¹² ∼7.33×10¹¹ eV^-1 cm^-2 respectively in measured temperature range. These results indicate that elevated temperature measurement is necessary to characterize GaN/AlGaN heterostructure based devices with oxide as gate dielectric.