| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 106 === In this thesis, we mainly focus on AlGaN/GaN High electron mobility transistor fabricated on Silicon substrate, hoping to operate at high power and high frequency conditions. Two types of structure were designed to enhance electric characteristic, one is Gate field plate structure, the other is Gate/Source dual field plate structure. These two structures were measured and analyzed by DC, breakdown voltage and high frequency characteristic to investigate the influence of device performance. In addition, different kinds of geometry layout were designed, including different Lg, Ldg, Lsg and field plate length, attempting to optimize the device performance.
We carried out lots of experiments in contact resistance, receiving the best ohmic contact resistance 0.5 Ω•mm with process parameter Ti /Al /Ni /Au = 25 /125 /45 /75 nm, RTA 850 oC 30 sec. Field plate structure were designed for better performance, the results showed that, for the device with Gate length (Lg) = 0.25 um, the maximum saturated current (Id max) and Transconductance (Gm) are 561 mA/mm, 161 mS/mm respectively, On-resistance is 5.16 Ω•mm. The break down voltage can increase from 310V to 390V via Gate/Source dual field plate structure, which can verify the dual field plate can enhance break down voltage compared with single field plate structure.
High frequency performances didn’t meet our expectation, The current gain cutoff frequency (fT) is 25 GHz and maximum frequency of available gain (fmax) of 16.5 GHz are achieved with 0.25μm gate length device
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