Influence of gate dielectric relative permittivity on polarization Coulomb field scattering in AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors

Abstract

AlGaN/GaN metal–insulator–semiconductor-high electron mobility transistors (MIS-HEMTs) with identical size parameters were fabricated using Si3N4 and ZrO2 as gate dielectrics, which have different relative permittivities. Based on experimental data and the Polarization Coulomb Field (PCF) scattering theory, the correlations among the additional polarization charges (ΔρG), the two-dimensional electron gas (2DEG) mobility, and the parasitic resistances (RS and RD) were quantitatively analyzed. This study reveals the underlying mechanism by which the gate dielectric relative permittivity modulates the PCF scattering and the electrical performance of the device. The results demonstrate that a higher gate dielectric relative permittivity alters the voltage partition between the dielectric layer and the AlGaN barrier. This alteration intensifies the vertical electric field within the barrier layer and induces more significant strain via the inverse piezoelectric effect. Consequently, a larger amount of ΔρG are generated, which notably reduces the under-gate electron mobility and modulates parasitic resistances. The enhanced PCF scattering further exacerbates the asymmetry of electron mobility in the source and drain access regions, resulting in an enlarged difference between per-unit-length values of RS and RD. This work provides a theoretical basis for the gate dielectric engineering of high-performance GaN-based MIS-HEMTs.