| Summary: | 碩士 === 國立虎尾科技大學 === 光電與材料科技研究所 === 97 === In recent years, the semiconductor fabrication was developed greatly. That is an important topic to get a high efficency device in the field of high frequency and high power device. Therefore, the researchs about devices were attended greatly by the research groups in the world. The high electron mobility transistor can get high electron mobility in the 2DEG, which located in the interface on AlGaN and GaN.
In this thesis, first, we will introduce the properties, applications of GaN and the fundamental of HEMT. The HEMT structure was grew by metal-organic chemical vapor deposition system. The sheet carrier demsity and electron mobility of the sample were 1.36×10^13 cm^-2 and 1200 cm^2/V-sec in room temperature. We referred the fundamental of ohmic contact to use the circular transmission line model. We can get the lower specific contact resistance 5×10^-4 Ω-cm^2 from Ti/Al/Ni/Au(30/150/45/55nm), which was annealed in nitrogen ambience 825℃ 30sec. The SiO2 sidewall passivation can avoid the mesa etching induced the sidewall leakage and prevent the drop height of mesa lead the gate metal not continue. When the fabrication of the devices was finished, we will measure the direct current properties of variouse gate length sizes devices. We can get the maximum saturation current 349 mA/mm and maximum transconductance 94 mS/mm.
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