Deep Electronic Levels of AlxGa1-xN with a Wide Range of Al Composition Grown by Metal–Organic Vapor Phase Epitaxy

Abstract

Deep electronic levels of AlxGa1-xN (0.25<x<0.60) were investigated by deep level transient spectroscopy (DLTS) and photocapacitance methods. Si-doped AlGaN layers were grown on an AlN/sapphire template by metal–organic vapor phase epitaxy. DLTS analysis using a sampling time window of up to 100 s showed two dominant deep levels with activation energies (ΔE) higher than 1.0 eV in AlxGa1-xN with x=0.25 and 0.37. The densities of those levels were higher than 1×1016 cm-3. For the Al0.60Ga0.40N sample, the deeper levels (ΔE>1.5 eV) were detected by photocapacitance measurement. It was found that the energy position of the dominant deep level closely followed the Fermi level stabilization energy reported by Walukiewicz et al. [J. Cryst. Growth 269 (2004) 119], indicating that the origin of the dominant deep level in AlGaN is related to a defect complex including anti-site defects and divacancies.