Narrow Results

This paper presents a detailed investigation of the effects of piezoelectricity, spontaneous polarization and charge density on the electronic states and the quasi-Fermi level energy in wurtzite-type semiconductor heterojunctions. This has required a full solution to the coupled Schrödinger–Poisson–Navier model, as a generalization of earlier work on the Schrödinger–Poisson problem. Finite-element-based simulations have been performed on a AlN/GaN quantum well by using both one-step calculation as well as the self-consistent iterative scheme. Results have been provided for field distributions corresponding to cases with zero-displacement boundary conditions and also stress-free boundary conditions. It has been further demonstrated by using four case study examples that a complete self-consistent coupling of electromechanical fields is essential to accurately capture the electromechanical fields and electronic wavefunctions. We have demonstrated that electronic energies can change up to approximately 0.5 eV when comparing partial and complete coupling of electromechanical fields. Similarly, wavefunctions are significantly altered when following a self-consistent procedure as opposed to the partial-coupling case usually considered in literature. Hence, a complete self-consistent procedure is necessary when addressing problems requiring more accurate results on optoelectronic properties of low-dimensional nanostructures compared to those obtainable with conventional methodologies.

Based on the first-principles, we simulated the spectral properties of PbWO₄ (PWO) crystals with an oxygen vacancy. As density functional theory (DFT) underestimates the band gap, the band edge is modified by Heyd-Scuseria-Ernzerhof (HSE). Moreover, artificial interactions of the charged defect of oxygen vacancies with three different charges have been corrected by finite-size correction scheme (FNV). Finally, the optical properties are obtained containing electron–phonon coupling. The calculated absorption band peaks of the F and F${}^{+}$ centers at 1.7eV and 2.47eV agree well with the experimental value, respectively.