Influence of the channel electric field distribution on the polarization Coulomb field scattering in In_0.18Al_0.82N/AlN/GaN heterostructure field-effect transistors

By making use of the quasi-two-dimensional (quasi-2D) model, the current-voltage (I-V) characteristics of In_0.18Al_0.82N/AlN/GaN heterostructure field-effect transistors (HFETs) with different gate lengths are simulated based on the measured capacitance-voltage (C-V) characteristics and I-V characteristics. By analyzing the variation of the electron mobility for the two-dimensional electron gas (2DEG) with electric field, it is found that the different polarization charge distributions generated by the different channel electric field distributions can result in different polarization Coulomb field scatterings. The difference between the electron mobilities primarily caused by the polarization Coulomb field scatterings can reach up to 1522.9 cm²/V· s for the prepared In_0.18Al_0.82N/AlN/GaN HFETs. In addition, when the 2DEG sheet density is modulated by the drain-source bias, the electron mobility presents a peak with the variation of the 2DEG sheet density, the gate length is smaller, and the 2DEG sheet density corresponding to the peak point is higher.