Shallow and deep defects in AlxGa1-xN structures

We report electrical characterization of AlGa1-xN materials grown by MOCVD. The techniques used in this study were admittance spectroscopy and photocurrent measurements. We identify a continuum of shallow donors with ionization energies ranging from 50 to 110 mcV in AlxGa1-xN alloys with values of the Al mole fraction x = 0. 1 and 0.3. Investigations of the photocurrent buildup kinetics allow identification of a deep center with optical ionization energy of 1.2 eV. This center controls the buildup of the photocurrent when the materials are illuminated with sub-bandgap photon energy. In the light of this finding we discuss the broad spectrum of DX-like defects that may contribute to the persistent photocurrent and the collapse in the drain current observed in AlGaN-related structures. (c) 2007 Elsevier B.V.. All rights reserved.