Optimization of ${\rm Al}_{0.29}{\rm Ga}_{0.71}{\rm N}/{\rm GaN}$ High Electron Mobility Heterostructures for High-Power/Frequency Performances

In this paper, we propose to optimize Al_0.29Ga_0.71N/GaN heterostructures on silicon substrate to obtain high electron mobility transistors featuring high-power/frequency performances. The polarization electric fields are engineered by varying the layer thicknesses of the cap and the barrier, and by changing the type of buffer (GaN or AlGaN). The aim of this paper is to find the best tradeoff between the active layer thickness reduction and the achievement of a reasonable drain current to satisfy the requirements for high performances. The optimum heterostructure device presents an output power density of 1.5 W/mm at 40 GHz, among the best reported on silicon substrate.