Photoionization Cross-Section in Tetrapod Quantum Dots: Impact of Pressure, Temperature, and Polarization Direction

This study investigates the photoionization cross-section (PCS) in GaAs-Ga_0.7Al_0.3As core–shell tetrapod quantum dot (CSTQD), elucidating its dependence on temperature, hydrostatic pressure, and polarization direction of incoming light. The intrinsic asymmetry of these nanostructures breaks rotational symmetry, rendering polarization dependence a critical parameter. Utilizing a theoretical framework rooted in the effective mass approximation (EMA) and numerical simulations performed with the finite element method (FEM), the electronic states are rigorously analyzed. The analysis extends to their influence on the binding energies (BEs) of the ground and first excited states, alongside the spatial distribution of electron probability densities within the nanostructure. Subsequently, the PCS variation across a range of pressures, temperatures, polarization directions, and impurity positions is systematically examined. The findings reveal that elevated temperature and pressure profoundly impact both the energy levels and the PCS for the two transitions under investigation. Specifically, the PCS undergoes a discernible blue shift (toward higher energies) with increasing pressure. Crucially, the PCS exhibits pronounced anisotropy concerning the polarization angle. This directional sensitivity underscores promising applications in polarization-selective optoelectronic devices and provides fundamental insights for the precise tuning of quantum dot-based photodetectors and sensors.