Dielectric engineering of electron mobility in asymmetric Coulomb-coupled GaN quantum wells with hybrid square-triangular confinement

Abstract This work investigates electron mobility in a non-tunneling, Coulomb-coupled GaN bilayer Q2DEG system with asymmetric confinement comprising an infinite-barrier square quantum well and an idealized semi-infinite Fang–Howard triangular-confinement channel. The model combines the distinct wave functions and form factors of the two wells with a three-region dielectric environment, finite-temperature bilayer RPA screening, and the linearized Boltzmann equation. Interface-roughness, charged-dislocation, dislocation-strain-field, and acoustic-phonon scattering are treated with static screening, whereas intrinsic longitudinal-optical-phonon and remote-optical-phonon scattering are treated inelastically with dynamic screening and the Rode iteration. The results show that at 1 K, the mobility is mainly limited by DCS and IRS, whereas LOP and ROP make negligible contributions. At 300 K, acS and LOP become important limiting mechanisms; LOP dominates at high density, whereas HfO₂ provides an additional clear ROP contribution at low density. For the same Sapphire outer regions, h-BN generally gives the highest total mobility, followed by Al₂O₃ and HfO₂, while replacing Sapphire with SiC produces only a relatively small difference. The effective electrostatic interlayer separation has a weak influence, whereas the SQW width strongly modifies IRS: at 1 K, the total mobility reaches a maximum near L = 90 Å; at 300 K, the mobility increases with L over the investigated range and is mainly limited by acS and LOP. An asymmetric density distribution between the two layers shifts or removes the IRS minimum and can increase the total mobility when the SQW layer carries the higher density. Within the investigated parameter range, the results clarify the coordinated roles of confinement shape, dielectric environment, well width, and carrier distribution in controlling transport in the GaN SQW–TQW system.