Deep-level defects in AlGaN/GaN heterostructures grown using rf-plasma-assisted molecular beam epitaxy

Abstract

Gallium nitride heterostructures sandwiched between AlGaN layers have been grown on sapphire substrates using rf-plasma-assisted molecular-beam epitaxy (MBE), and their electrical properties investigated. Deep-level transient spectroscopy (DLTS) measurements reveal that the activation energies of the two electron levels were 0.21 eV and 0.23 eV relative to the conduction band, with capture cross sections of 5.0 x 10-15 cm2 and 7.4 x 10-17 cm2, respectively. From the capture kinetics of the deep-level defects, according to the filling pulse duration and the bias voltage, it is suggested that the 0.21 eV defect is associated with nitrogen vacancies and the 0.23 eV defect is associated with extended defects.