The influence of the channel electric field distribution on the polarization Coulomb field scattering in AlN/GaN heterostructure field-effect transistors

Based on the measured capacitance—voltage (C—V) curves and current—voltage (I–V) curves for the prepared differently-sized AlN/GaN heterostructure field-effect transistors (HFETs), the I–V characteristics of the AlN/GaN HFETs were simulated using the quasi-two-dimensional (quasi-2D) model. By analyzing the variation in the electron mobility for the two-dimensional electron gas (2DEG) with the channel electric field, it is found that the different polarization charge distribution generated by the different channel electric field distribution can result in different polarization Coulomb field (PCF) scattering. The 2DEG electron mobility difference is mostly caused by the PCF scattering which can reach up to 899.6 cm2/(V·s) (sample a), 1307.4 cm2/(V·s) (sample b), 1561.7 cm2/(V·s) (sample c) and 678.1 cm2/(V·s) (sample d), respectively. When the 2DEG sheet density is modulated by the drain—source bias, the electron mobility for samples a, b and c appear to peak with the variation of the 2DEG sheet density, but for sample d, no peak appears and the electron mobility rises with the increase in the 2DEG sheet density.