First-Principles Investigation of Electronic and Phonon Properties of Wurtzite Semiconductors for Nigerian Solar Cell Applications

Wide band gap wurtzite semiconductors including gallium nitride, indium nitride, and their alloys offer tuneable direct band gaps ideal for multi-junction solar cell applications covering the full solar spectrum. Understanding their electronic band structures and phonon dynamics from first principles is essential for optimising photovoltaic device performance. This study conducts a first-principles investigation of the electronic structure, phonon dispersion, and electron-phonon coupling in wurtzite GaN, InN, and In-xGa-1-x-N alloys using density functional theory within the generalised gradient approximation and hybrid HSE06 functional. The Vienna Ab initio Simulation Package is used for electronic structure calculations. Phonon dispersion curves are computed using density functional perturbation theory with the Phonopy code. Electron-phonon coupling coefficients governing charge carrier mobility are extracted using the EPW code implementing the Wannier interpolation of electron-phonon matrix elements. The computed band gaps of GaN (3.41 eV) and InN (0.72 eV) agree with experimental values within 3 percent using HSE06. Carrier mobility in InGaN alloys decreases by a factor of 4 between 10 and 50 percent indium content due to alloy disorder scattering. Band alignment calculations at InGaN-GaN interfaces predict Type I band offsets suited for carrier confinement in multi-junction devices. Keywords: first-principles, wurtzite semiconductor, phonon dispersion, electron-phonon coupling, solar cell