Unpinned (100) GaAs surfaces in air using photochemistry

We have unpinned the Fermi level at the surface of both n‐ and p‐type (100) GaAs in air. Light‐induced photochemistry between GaAs and water unpins the surface Fermi level by reducing the surface state density. Excitation photoluminescence spectroscopy shows a substantial decrease in both surface band bending and surface recombination velocity in treated samples, consistent with a greatly reduced surface state density (≂1011 cm−2). Capacitance‐voltage measurements on metal‐insulator‐semiconductor structures corroborate this reduction in surface state density and show that the band bending may be controlled externally, indicating an unpinned Fermi level at the insulator/GaAs interface. We discuss a possible unpinning mechanism.

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