Band bending near the surface in GaN as detected by a charge sensitive probe


We measured the absolute value of the surface band bending in GaN layers grown by molecular beam epitaxy with a charge sensitive surface microprobe. Surface potential measurements showed an upward band bending from 0.7 to 1.4 eV in undoped and Si-doped GaN. The samples stored in dark for one week showed an increase in band bending by up to 0.1 eV. The effect of ultraviolet (UV) exposure (with a lamp or a pulsed nitrogen laser) on band bending was also studied. Typically, the surface barrier decreased by about 0.2–0.5 eV under UV light. The barrier was restored very slowly (by a logarithmic law) in the dark at room temperature. These and other similar phenomena are tentatively attributed to thermionic transfer of free electrons from the bulk to the surface states. Photo-induced desorption of oxygen may also play a role in the observed effects.

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This work was funded by AFOSR (Dr. G. L. Witt), NSF (Dr. L. Hess and Dr. U. Varshney), and ONR (Dr. C. E. C. Wood and Dr. Y. S. Park).

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Correspondence to S. Sabuktagin.

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Sabuktagin, S., Reshchikov, M.A., Johnstone, D.K. et al. Band bending near the surface in GaN as detected by a charge sensitive probe. MRS Online Proceedings Library 798, 542–547 (2003).

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