Electro-optic investigation of the surface trapping efficiency in n-alkanethiol SAM passivated GaAs(001)

摘要

The electro-optic characteristics of the semi-insulating and n ~+-type GaAs(001) surfaces passivated with n-alkanethiol self-assembled monolayers were investigated using Kelvin probe surface photovoltage (SPV) and photoluminescence (PL) techniques. Referencing the equilibrium surface barrier height established in an earlier report, SPV measurements demonstrated a significant (>100mV) increase in the non-equilibrium band-bending potential observed under low-level photo-injection. Modeling of the SPV accounts for these observations in terms of a large (>10~4) decrease in the hole/electron ratio of surface carrier capture cross-sections, which is suggested to result from the electrostatic potential of the interfacial dipole layer formed upon thiol chemisorption. The cross-section effects are verified in the high-injection regime based on carrier transport modeling of the PL enhancement manifested as a reduction of the surface recombination velocity.