Modeling of 2DEG and 2DHG in i-GaN capped AlGaN/AlN/GaN HEMTs

A 2D drift-diffusion model with Schrodinger-Poisson quantum corrections using ATLAS toolbox by Silvaco is calibrated against experimental I_D-V_GS characteristics of the 1 μm gate length GaN-based high electron mobility transistor (HEMT). The model takes into account both piezoelectric and spontaneous polarization effects at the all interfaces of GaN/Al_0.25Ga_0.75N/AlN/GaN structure. This unintentionally doped hetero-structure transistor has i) an enhanced carrier mobility due to the decrease in alloy-disorder and impurity scatterings; ii) an increased carrier sheet density in 2DEG due to a better confinement in the channel thanks to AlN spacer. These improvements considerably enhance the output power and performance of the GaN HEMTs. We found that surface traps play an essential role in the creation of 2DHG which can affect a carrier density in 2DEG.