Empirical tight-binding parameterizations for transferable semiconductor alloy and heterostructure calculations

This thesis focuses on the development and application of the empirical tightbinding (ETB) method for transferable calculations of semiconductor alloys and heterostructures. The primary objective is to demonstrate the capability of a recently proposed ETB scheme in accurately reproducing experimental observations and providing valuable insights into the underlying physics of these complex systems. The theoretical foundation of the ETB method is discussed, with a focus on a recently proposed scheme and its advantages over other older ETB schemes in terms of strain treatment and transferability. The new scheme is applied to study various semiconductor alloy systems, including GaAsSb, InAsSb, and InGaSb. The large-supercell simulations are performed to investigate the impact of alloy fluctuations on the electronic and optical properties of GaAsSb, revealing the asymmetric roles of Sb and As nonuniformity. The ETB results are compared with experimental data, validating the accuracy of the scheme and providing insight into the role of the alloy fluctuations. The new scheme is also employed to simulate semiconductor heterostructures, such as the short-period InAs/GaSb type-II superlattice and the triple-barrier resonant-tunneling structure. The ETB results are compared with experimental data and other theoretical approaches, evaluating the reliability of the new ETB scheme for heterostructure simulations. A key contribution of this thesis is the development of an efficient and easy-to-use parameterization procedure for the new ETB scheme. The challenges associated with parameterizing complex ETB schemes are addressed, and a systematic strategy combining multi-objective optimization algorithms with a physically motivated staging approach is proposed. The effectiveness of this strategy is demonstrated through a case study of GaN parameterization, yielding promising results for GaN in both zincblende and wurtzite phases as well as in the dilute-nitride GaNAs alloy. This thesis contributes to the advancement of theoretical modeling of semiconductor alloys and heterostructures, suggesting a reliable tool for the atomistic simulation of these complex systems. The developed parameterization strategy popularizes the use of sophisticated ETB methods, enabling researchers to harness the power of these tools to study novel materials and devices. This work paves the way for the rational design and optimization of optoelectronic devices.