Demonstration of acceptor-like traps at positive polarization interfaces in Ga-polar p-type (AlGaN/AlN)/GaN superlattices

Abstract

This study experimentally shows the existence of acceptor traps at positive polarization interfaces acting as the source of holes in Ga-polar p-type uniformly doped (AlGaN/AlN)/GaN superlattices with low Mg doping. The observed hole concentrations which exceed that of the dopants (here, Mg) incorporated into the samples during growth, can be explained by the ionization of acceptor traps, placed 0.8 eV above the valence band of GaN, at positive polarization interfaces. All samples were epitaxially grown using Metal Organic Chemical Vapor Deposition, and were characterized using X-Ray Diffraction and room-temperature Hall measurements. The measured hole concentrations are compared to calculated values from STR FETIS® and the measured mobility trends are explained using the separation of the positive polation interfaces from the two-dimensional hole gas in the systems, strengthening the hypothesis.