Tuning Interfacial Phonon Transport in GaN/WSSe van der Waals Heterostructure toward High-Efficiency Thermoelectric Performance

The thermoelectric performance of Gallium Nitride (GaN) is inherently limited by its relatively high thermal conductivity and low electrical conductance and thus subsequently decreases its efficiency for power generation from thermal differences. To overcome these limitations, we propose the GaN/WSSe vdW Heterostructure to lower the thermal lattice conductivity and enhance efficiency. Our present work utilizes density functional theory (DFT) to explore structural, electronic, and thermal transport characteristics. The stability of both the monolayer and bilayer structures has been evaluated by analyzing their energetic and thermodynamic stability. The adhesion energy was calculated for the bilayer to verify the most stable stacking model of the GaN/WSSe. The Se-4 and S-3 stacking model has the highest adhesion energies of -508 and -663 meV, respectively, and exhibits staggered (type-II) band alignment, enabling the separation of charge carriers at the interface. Furthermore, the thermoelectric transport characteristic has been analyzed using the nonequilibrium Green's function (NEGF) formalism with the Landauer-Büttiker framework, which describes ballistic quantum transport. The electronic transport channels at the interface suppress the electron scattering, causing a higher G_e of vdWHs and also intermediate thermopower between |S|_GaN and |S|_WSSe. The Se-4 and S-3 vdWHs enhance the phonon scattering, leading to a decrease in phonon thermal conductance (κ_ph) and consequently resulting in high ZT values of 3.99 and 4.23 having been achieved at higher temperatures. The findings indicate that the GaN/WSSe vdWH holds significant potential for thermoelectric applications.