Abstract
We studied restoration of the band bending at the surface of undoped GaN layers after illumination with pulses of the above-bandgap light. The absolute value of band bending and transients of the photovoltage were measured with an atomic force microscope in the surface potential mode (Kelvin probe method). The photovoltage transients following very weak excitation with a single pulse of light could be well fitted within a simple phenomenological model accounting for charging of the acceptor-like surface states by free electrons after the light pulse. Photo-induced desorption of ions at the surface and recharging of a surface oxide layer may also affect the value and transients of the photovoltage, particularly if the illumination is prolonged. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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