Investigation of oxygen incorporation in AlGaN/GaN heterostructures

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 °C 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. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)