PhD thesis supervisor: dr. Evelina Dudutienė (apply for recommendation)
Optical study of GaAsBi quantum structures
Currently, the Optoelectronics Department actively investigates GaAsBi semiconductor materials for use as the active medium in lasers operating in the NIR spectral range. GaAsBi quantum structures offer potential to develop NIR lasers on a GaAs platform, exhibiting weak temperature dependence of the emission wavelength, which is crucial for enhancing device performance. However, incorporation of Bi into the crystal lattice during MBE remains a technological challenge, limiting emission intensity of GaAsBi quantum structures and requiring optimization of growth parameters and structural design. Understanding the mechanisms limiting emission demands a detailed study of how optical and electronic properties of GaAsBi quantum structures depend on Bi concentration, growth conditions, and structural design.
Despite significant progress, many fundamental questions remain unresolved, particularly regarding carrier localization and the factors influencing it, as well as IQE, with emphasis on carrier recombination mechanisms in quantum structures. Systematic studies of optical properties in structures with Bi concentrations above 5% are especially lacking, even though such concentrations are required to achieve longer NIR wavelengths. This work will conduct comprehensive optical studies of GaAsBi quantum structures across a wide Bi concentration range (up to ~10%), closely integrating optical characterization with growth technology.