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

Abstract

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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Acknowledgments

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). https://doi.org/10.1557/PROC-798-Y5.39

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