Surface-Passivation-Enabled Electronic and Optical Property Engineering in Two-Dimensional GaSb.

Abstract

Gallium antimonide (GaSb) is promising for next-generation electronics and optoelectronics due to its high carrier mobility and narrow bandgap (∼0.725 eV). However, in two-dimensional (2D) form, surface dangling bonds cause instability and Fermi-level pinning, degrading performance. We show that hydrogen (H) and halogen (F, Cl, Br) passivation not only stabilizes 2D GaSb but also precisely modulates its electronic and optical properties. First-principles calculations reveal the following: (1) Passivation induces electron depletion, with charge transfer following electronegativity (H < Br < Cl < F); (2) it converts the bandgap from indirect to direct; and (3) it systematically increases the bandgap, electron affinity, and ionization energy by eliminating surface states and enhancing orbital hybridization. Optically, Cl/Br passivation significantly boosts absorption and joint density of states, while H/F induces minimal changes. These insights establish passivation as a dual-purpose strategy for stabilizing and property-tuning 2D GaSb, enabling its integration into advanced semiconductor devices.