Thermomagnetic transport and field-tunable figures of merit in GaAs/AlGaAs superlattices

Herein, we present a comprehensive theoretical and computational investigation of both the longitudinal (ZT_xx) and off-diagonal (ZT_xy) thermoelectric performance of GaAs–AlGaAs superlattices subjected to combined alternating electric and perpendicular magnetic fields. Using the semiclassical Boltzmann transport framework, the model incorporates miniband electron dynamics, impurity and phonon scattering, donor activation, and both electronic and lattice contributions to heat transport. The applied magnetic field couples the longitudinal and transverse channels, giving rise to non-zero off-diagonal thermopower (α_xy) and electrical conductivity (σ_xy) components, while simultaneously modifying the longitudinal thermoelectric response (α_xx, σ_xx). Parametric analyses across temperature, miniband width, carrier density, chemical potential, and lattice thermal conductivity reveal that quantum confinement and magneto-thermoelectric coupling can substantially enhance both ZT_xx and ZT_xy, with the transverse component showing particularly strong gains at moderate magnetic fields at sub-room temperatures. These results demonstrate the potential of engineered GaAs–AlGaAs superlattices for high-efficiency longitudinal and transverse thermoelectric energy conversion, providing a predictive framework for optimising anisotropic thermoelectricity in low-dimensional semiconductor systems.