GaAsBi structures for ultrafast optoelectronics grown at different Bi fluxes

Abstract

 GaAsBi is an attractive semiconductor material for the development of infrared optoelectronics devices due to possibilities of band engineering when, varying the Bi content, one can induce a rapid rising of the valence band edge. Although this property makes GaAsBi a promising material for terahertz (THz) emitters, telecommunication lasers, and low noise photodetectors, the yield of the developed GaAsBi-based devices is still low indicating a requirement for the better quality of the material. In this work, we extend previous studies focusing on the investigation of the influence of Bi flux during the molecular beam epitaxy growth. The structures were characterized using high-resolution X-ray diffraction, photoluminescence and optical pump–THz probe technique. It is shown that multiple growth runs targeting at the ~6% Bi content and near-infrared operation wavelength of around 1.2µm yielded consistent structural and optical properties, indicating that the optimal and repeatable growth protocol has been successfully established. The observed red-shifts in photoluminescence spectra and the bi-exponential decay in carrier relaxation can be associated with the existence of band-tail states and random potential due to fluctuations in the distribution of Bi content.