Demonstration of Acceptor-Like Traps at Positive Polarization Interfaces in Ga-Polar P-type (AlGaN/AlN)/GaN Superlattices

Abstract

The shortcomings with acceptors in p-type III-nitride semiconductors have resulted in not many efforts being presented on III-nitride based p-channel electronic devices (here, field effect transistors (FETs)). The polarization effects in III-nitride superlattices (SLs) lead to the periodic oscillation of the energy bands, exhibiting enhanced ionization of the deep acceptors (Mg in this study), and hence their use in III-nitride semiconductor-based light-emitting diodes (LEDs) and p-channel FETs is beneficial. This study experimentally demonstrates the presence of acceptor-like traps at the positive polarization interfaces acting as the primary source of holes in Ga-polar p-type uniformly doped (AlGaN/AlN)/GaN SLs with limited Mg doping. The observed concentration of holes exceeding that of the dopants incorporated into the samples during growth can be attributed to the ionization of acceptor-like traps, located at 0.8 eV above the valence band of GaN, at positive polarization interfaces. All samples were grown using the metal organic vapor phase epitaxy (MOVPE) technique, and the materials’ characterization was carried out using X-ray diffraction and Hall effect measurements. The hole concentrations experimentally measured are juxtaposed with the calculated value of hole concentrations from FETIS®, and the measured trends in mobility are explained using the amplitude of separation of the two-dimensional hole gas in the systems from the positive polarization interfaces.