Metal-Insulator-Semiconductor Diode Characterization on n-GaN by Capacitance-Voltage Measurement at 150 degrees C Metal–Insulator–Semiconductor Diode Characterization on n-GaN by Capacitance–Voltage Measurement at 150 °C

GaN metal–insulator–semiconductor (MIS) diodes (MISDs) were evaluated with capacitance–voltage ($C$–$V$) measurement at 150 °C and under UV light illumination. From $C$–$V$ scan at 150 °C, a high density of SiO2/GaN interface traps was found to pin the semiconductor surface potential ($\varPhi_{\text{S}}$) at 0.7–0.9 eV. At $-20$ V, transient capacitance measurement was performed at 150 °C under dark condition or after 5 min UV light illumination. From the transient measurements, $\varPhi_{\text{S}}$ of the steady status was measured to be 4.2 eV, which is much larger than the band gap of GaN, indicating that no thermal equilibrium was achieved at the steady status. The reason for the absence of thermal equilibrium was discussed. It was suggested that the leakage through the oxide is too large compared with the electron–hole generation rate in this wide-band-gap semiconductor. The insulative properties of conventional insulators should be reevaluated for wide-band-gap semiconductors.