Atomistically resolved density functional modelling of GaInPSeS quantum dots

Semiconductor quantum dots (QDs) exhibit size-dependent and composition-dependent electronic properties governed by quantum confinement, atomic scale disorder, and surface termination. A quantitative understanding of how these factors shape the electronic structure of multicomponent QDs remains essential for their application in nanoscale electronic systems. In this work, atomistically resolved density functional modelling was used to investigate the electronic structure of compositionally disordered GaInPSeS QDs. Finite QDs were constructed from a zincblende GaP parent lattice with mixed cation and anion substitution and were geometry optimised using a semiempirical quantum mechanical approach. Hydrogen passivated QDs were generated by saturating undercoordinated surface sites and were subsequently geometry optimised using the same method to obtain relaxed passivated configurations. The optimised unpassivated and passivated structures were used as inputs for plane wave density functional theory (DFT) calculations to obtain the total density of states (TDOS) and atom-resolved projected density of states (PDOS). The results showed a dense deep valence electronic manifold that remained largely unchanged upon surface termination, while the electronic states closest to the Fermi level were strongly influenced by surface atoms and local coordination environments. Atom resolved analysis showed that cation derived states remained confined to deeper valence energies, whereas anion species dominated the electronic structure near the Fermi level. In particular, Se exhibited stronger variability near the Fermi level compared to S, indicating element dependent surface electronic behaviour. Surface and core resolved DOS analysis showed that surface atoms contributed significantly near the Fermi level in the unpassivated QDs, while hydrogen passivation reduced this contribution through redistribution of near-edge spectral weight. These results established a physically grounded electronic structure framework that captures the interplay between compositional disorder and surface termination in GaInPSeS QDs and provides atomistic insight relevant to the design and interpretation of multicomponent QD systems.