Variation of structural and optical properties across an AlGaN/GaN HEMT structure directly imaged by cathodoluminescence microscopy

Abstract

Non-planar selective area growth of GaN and Al0.1Ga0.9N was performed by metalorganic chemical vapor deposition, on selectively etched GaN samples masked with SiO2-ridges. We report on the characterization of this lateral structured AlGaN/GaN HEMT structure using spatially and spectrally resolved cathodoluminescence. A distinct change of emission energy of the AlGaN and GaN across the ridge was observed. The shift of AlGaN emission directly visualizes the strong lateral Al composition gradient across the ridge. The modulation of emission energy of the two dimensional electron gas (GaN emission) leads to the formation of a potential well with distinct barriers in the slope region and a pronounced lateral confinements inside of the well at the ridge edges. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)