INVESTIGATION OF OXYGEN INCORPORATION IN ALGAN/GAN HETEROSTRUCTURES

Abstract

The unintentional doping of oxygen atoms in undoped AlGaN layers was demonstrated by scanning photoemission microscopy (SPEM) using synchrotron radiation. In-situ annealing at 1000 degreesC and subsequent SPEM imaging showed that the oxygen concentration in AlGaN was much higher than in GaN. Space-resolved photoemission spectra of O 1s, Ga 3d and Al 2p core levels showed that the predominant oxygen incorporation in AlGaN resulted from the formation of Al-O bonds due to the high reactivity of Al with oxygen. The degenerated AlGaN layer produced by the oxygen donors caused the tunneling-assisted transport of electrons at the interface of the AlGaN with metal contacts and an increase in the sheet carrier concentration at the AlGaN/GaN heterointerface. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim