stics, better heat dissipation capability (approximately 1.5 times of GaAs substrate), and higher peak electron velocity, allowing higher performance at lower voltages. Although InP/InGaAs HBT with lattice matching on the InP substrate has superior high-frequency and high-speed characteristics, and lower turn-on voltage than GaAs HBT, it suffers from small substrate size, high cost, and fragility of the InP substrate, limiting its large-scale and low-lost production. The capability to obtain high-quality and large-size semi-insulating InP substrate is the key to lower cost. Therefore, to meet the increasing demand for InP devices, the fundamental task is to grow high-quality and large-diameter InP single crystal substrate [26]. There is a growing interest in GaAs mHEMT technology due to the cost, fragility, and pro- cess compatibility issues of InP substrates. The GaAs mHEMT technology grows a rela- tively thick InAlAs layer between the channel and the GaAs substrate. The composition of indium changes from a positive value to zero, thus the mismatch of the lattice is alleviated. After adding a buffer layer with graded component, the component percentage of indium in the channel layer can be chosen almost arbitrarily between 30% and 60%, and the device performance is optimized with a great degree of freedom. The mHEMT can be considered as InP HEMT technology on GaAs substrate. It shows superior performance relative to InP in terms of low noise, allowing GaAs to solidify its position at the low-end of mmWave fre- quencies, and further its way into the high-end range of mmWave spectrum [26]. A 220-320 GHz mHEMT MMIC amplifier was reported in the literature using high indium composition in InGaAs as channel to achieve high-carrier density and mobility. Double InAlAs barrier layers and bilateral delta doping are designed to increase channel electron confinement and to reduce contact resistance. The buffer layer with linear component change is used to achieve lattice matching. The fT and fmax are 515 and 700 GHz, respe