Piezoelectric polarization and quantum size effects on the vertical transport in AlGaN/GaN resonant tunneling diodes**Project supported by the Deanship of Scientific Research of University of Dammam (Grant No. 2014137).

Abstract

In this work, the electronic properties of resonant tunneling diodes (RTDs) based on GaN-AlxGa(1−x)N double barriers are investigated by using the non-equilibrium Green functions formalism (NEG). These materials each present a wide conduction band discontinuity and a strong internal piezoelectric field, which greatly affect the electronic transport properties. The electronic density, the transmission coefficient, and the current–voltage characteristics are computed with considering the spontaneous and piezoelectric polarizations. The influence of the quantum size on the transmission coefficient is analyzed by varying GaN quantum well thickness, AlxGa(1−x)N width, and the aluminum concentration xAl. The results show that the transmission coefficient more strongly depends on the thickness of the quantum well than the barrier; it exhibits a series of resonant peaks and valleys as the quantum well width increases. In addition, it is found that the negative differential resistance (NDR) in the current–voltage (I–V) characteristic strongly depends on aluminum concentration xAl. It is shown that the peak-to-valley ratio (PVR) increases with xAl value decreasing. These findings open the door for developing vertical transport nitrides-based ISB devices such as THz lasers and detectors.