Laser-induced surface potential transients observed in III-nitride heterostructures
- 16 September 2002
- journal article
- research article
- Published by AIP Publishing in Applied Physics Letters
- Vol. 81 (12) , 2282-2284
- https://doi.org/10.1063/1.1506416
Abstract
We report on very long surface potential transients induced by ultraviolet laser illumination, which have been observed in nitride heterostructures. These surface potential transients correlate with current transients when measured simultaneously. Under illumination, electron–hole pairs are generated, which screen the electric field in the AlGaN barrier layer causing the surface potential to decrease. The holes move toward the surface assisted by the electric field in the AlGaN while the electrons increase the sheet charge concentration at the AlGaN/GaN interface, decreasing the net charge dipole across the barrier layer. This reduction can cause the surface potential to vary as much as 1 V between the unilluminated and illuminated states. The long transient response observed after the laser is turned off is explained by the slow recombination of the holes with the electrons thermionically emitted from the potential well at the interface. The thermionic emission is modeled by a continuously varying barrier potential, which results in a stretched exponential-type response.Keywords
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