Fig. 4: Theoretical and experimental illustrations on the mechanism of passivation improvements.

a Schematic of near-surface sample structure and corresponding simulated surface-induced electric field versus distance from the sample surface. The range of the Bohr radius⁴¹ is marked in yellow, and the electric field intensity decreases significantly after passivation. b Simulation of the conduction and valence bands in the structure at T = 4.0 K. The surface band-bending decreases significantly after passivation. c Ga 2p, d As 3d XPS spectra, and e Raman spectra of GaAs (001) surface treating under different passivation techniques. The “untreated” is the reference group. The ODT (1-Octadecanethiol) passivation is conducted through immersion in a 0.05 mol L⁻¹ ODT solution. The ALD passivation is performed by 10 nm Al₂O₃ coating using ALD. “wet-S” and “dry-S” passivation are achieved through immersion in (NH₄)₂S solution and exposure to vapor phase H₂S, respectively. The “wet-S + ALD” group uses the same passivation techniques in this article, demonstrating the best improvements compared to other techniques. Details concerning four passivation techniques are illustrated in Supporting Information IX