The relationship between AlGaN barrier layer thickness and polarization Coulomb field scattering in AlGaN/GaN heterostructure field-effect transistors

Abstract Identically-sized AlGaN/GaN HFETs were fabricated on three AlGaN/GaN heterostructure with differing AlGaN barrier layer thicknesses of 15.5 nm, 19.3 nm and 24.7 nm. Based on polarization Coulomb field (PCF) scattering theory, additional polarization charges and electron mobility under the gate were calculated, and the relationship between AlGaN barrier layer thickness and P C F scattering in AlGaN/GaN H F E T s was determined. For the AlGaN/GaN H F E T s with a thicker AlGaN barrier layer, when the same gate bias was applied to the gate, the inverse piezoelectric effect (IPE) of the barrier layer was weaker, resulting in fewer additional polarization charges. The AlGaN/GaN H F E T s with a thicker AlGaN barrier layer also possessed a higher 2DEG sheet charge density, diminishing the P C F scattering intensity. It can be concluded that increasing the AlGaN barrier layer thickness reduces the IPE and raises the 2DEG sheet charge density, both of which decreases the PCF scattering intensity. The results of this study have guiding value toward the optimization of AlGaN/GaN HFETs materials and structures.