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• Main Authors: Zhen-Wei Liu, 劉鎮瑋
• Other Authors: Yue-Ming Hsin
• Format: Others
• Language: en_US
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/d42xj7

碩士 === 國立中央大學 === 電機工程學系 === 105 === GaN based devices are suitable candidates of low on resistance and high breakdown device because of high electron velocity and breakdown field in GaN materials. The major applications include RF power amplifiers and power switching. However, there is a serious current collapse problem when transistor operated as a switch in high frequencies. The main cause is due to epitaxial layer quality, which effects in AlGaN/GaN and buffer layers act like traps which traps carriers and results in current collapse leading to a great impact on the DC and RF characteristics. This study analyzes device current collapse phenomenon using commercial GaN HEMT in small-signal model and gate-lag/drain-lag measurement. In small signal equivalent circuit modeling, extracted values of intrinsic elements in leaner and saturation regions were compared after different high-voltage off-state biases. The significant change in the intrinsic elements after high-voltage off-state biases are channel resistance (Rds) and gate-drain capacitance (Cgd), which may attribute to the GaN channel and buffer layers. Besides, small signal equivalent circuit model after high-voltage off-state was investigated under different temperatures. Gate-lag and drain-lag were measured at different temperatures to study the trapping effect. Because of temperature effect, trapping effect is alleviated at higher temperature thus current collapse is less severe. . Finally, a thermal storage was carried out on GaN HEMTs at 150 C under room temperature ambient. No degradation was found after 55 hours storage.