| Summary: | 碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 93 === In this thesis, the characteristics of the In0.425Al0.575As/InxGa1-xAs metamorphic high electron mobility transistors (MHEMT’s) with two different channel designs, grown by a molecular beam epitaxy (MBE) system have been studied. The studied devices exhibit high-frequency circuit applications, including the drain-source saturation current density (IDSS = 511 mA/mm), maximum extrinsic transconductance (gm,max =315 mS/mm), microwave performance (fT = 55.4 GHz, and fmax = 77.5 GHz), and low-noise characteristics (NFmin=0.88 dB at 2.4 GHz) have been achieved for the pseudomorphic channel MHEMT (PC-MHEMT). Therefore, PC-MHEMT is suitable for high-frequency and low-noise applications. On the other hand, due to higher conduction-band discontinuities (ΔEc) and good carrier confinement, the high-temperature device characteristics with good thermal stability is achieved for the deviations of IDSS and gm,max are 21.9﹪and 17.7﹪with increasing the temperature from 300 K to 500 K, respectively. In addition, the V-shaped symmetrically-graded channel MHEMT (SGC-MHEMT) due to the effective energy-gap is larger than that of PC-MHEMT, improved breakdown characteristics (BVGD =
-16.05 V, BVoff = 14.64 V, and BVon=10.9 V) and the deviations of BVGD is 26﹪ with increasing the temperature from 300 K to 500 K. Therefore, SGC-MHEMT is suitable for high-power and high-linearity circuit applications, including improved gate-voltage swing (GVS = 1.3 V), small-signal power gain (Gs =19.2 dB), and output power (Pout =14.9 dBm).
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