| Summary: | 碩士 === 國立交通大學 === 照明與能源光電研究所 === 103 === AlGaN/GaN HEMTs have high electron mobility, high saturation velocity and high breakdown, comparing with other electron device. AlGaN/GaN HEMTs have been wide applications for high frequency and high power densities. However, their performance is limited by current collapse. The surface passivation layer has shown remarkable improvement in reducing the current collapse effect.
Compared with those of SiNx, AlN thin film has a larger band-gap (6.2 eV), which can suppress traps to surface. DC and pulse IV measurement results are used to compare with AlGaN/GaN HEMTs with SiNx passivation layer .The results indicated that AlGaN/GaN HEMTs with AlN passivation layer, larger current-gain cutoff frequency (fT) and maximum oscillation frequency (fmax). Beside, small signal equivalent circuits are used to extract variation of intrinsic capacitance. AlGaN/GaN HEMTs with AlN passivation layer has small intrinsic capacitances. Complementary, the wet chemical treatments of AlGaN surface prior to deposition AlN passivation layer can reduce surface roughness and the presence of dangling bond (Ga-O). It can improve the device performance.
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