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Transient Photovoltage In Gan As Measured By Atomic Force Microscope Tip, M. A. Reshchikov, S. Sabuktagin, D. K. Johnstone, H. Morkoç

Electrical and Computer Engineering Publications

We studied restoration of the band bending at the surface of undoped GaN layers after illumination with above-bandgap light. The photovoltage saturated with illumination at about 0.2–0.3 eV at room temperature, although the upward band bending for GaN in the dark is of the order of 1 eV. We attribute the photovoltage effect to charging of the surface states, the density of which is estimated at about 10^12 cm^−2. Restoration of the barrier after a light pulse is simulated by a phenomenological model whereby the acceptorlike surface states are emptied of electrons under illumination and filled back in dark due …