Mechanistic Insights into the Chemical and Electronic Doping for Advanced Optoelectronic, Catalytic, and Quantum Applications

PhD;2023;Materials Research Centre

Doping via the incorporation of ionizable entities within solid-state materials represents a promising strategy for the generation of mobile or localized charge carriers. Conventionally, doping has been perceived as an atomistic process involving the chemical substitution of host atomic sites with impurities. Nevertheless, an alternative mechanism such as polaron formation involves electronic perturbations that give rise to defect levels within the band gap without the need for substitutional impurities. Shallow defects, in particular, play a pivotal role in facilitating the availability of free charge carriers, whereas deep center defects exhibit substantial potential for a wide range of optoelectronic applications. The intricate nature of successful doping is further compounded when materials with unique quantum mechanical interactions and correlations come into consideration. Therefore, a mechanistic understanding of doping is imperative for the advancement of optoelectronics, catalysis, and quantum technologies. Using first-principles density functional theory with an effective U approach and hybrid functional study, we unravel several mechanistic insights into the chemical and electronic doping in semiconductor and developed different design strategies for preferred applications. We unravel the origin of low mobility by investigating adiabatic and non-adiabatic migration of electron polarons in β-TaON. Further, we established the correlation between self-trapped hole polaron relaxation dynamics and broadness in photoluminescence spectra of ultra-wide-band gap oxide LiGaO2. Additionally, we uncover the role of polarons in nitrogen reduction in TiO2 photocatalysts. Next, we investigated the thermodynamics and diffusion mechanism of carbon and iron defects in GaN for quality improvement of AlGaN/GaN-based high-electron mobility transistor. We also discovered that carbon doping with Stone-Wales defect in 2D hexagonal boron nitride acts as a single-photon emitter for quantum information applications. Moreover, we present quantum-confinement effect driven strategy for controlling defect levels by varying the diameter of 1D-VO2 nanowires. By unravelling the intricacies of doping and optimizing defect levels for specific applications, this research paves the way for diverse applications in modern electronic technologies.