PhD thesis supervisor: dr. Saulius Tumėnas (apply for recommendation)
Impact of spontaneous CuPt-type atomic ordering on electronic structure of bismides
This research aims to elucidate the fundamental mechanisms of spontaneous CuPt-type atomic ordering and its influence on the electronic structure and optical response of GaAsBi bismides. Spectroscopic ellipsometry (SE) measurements (0.7-6.0 eV) will be performed in conjunction with polarised photoluminescence (PL) and modulation spectroscopy techniques across a comprehensive compositional range (x = 0.01-0.1) and temperature interval (T = 3-350 K). The investigation will systematically examine: (i) the ordering-induced valence band splitting; (ii) temperature-dependent evolution of optical anisotropy; (iii) impact on high-energy critical points; and (iv) manifestation in quaternary GaInAsBi alloys. Theoretical analysis will employ density functional theory (DFT) calculations with hybrid functionals and empirical pseudopotential methods to develop a comprehensive model of the ordered bismide electronic structure. Additionally, the study will investigate the effects of ordering on the THz-pulse emission efficiency via optical orientation of photoelectrons. This research addresses critical gaps in understanding bismide physics while supporting their development for IR, MIR, and THz optoelectronic applications.