Numerical analysis of transmission coefficient, LDOS, and DOS in superlattice nanostructures of cubic $$\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}$$ Al x Ga 1 - x N/GaN resonant tunneling MODFETs

Abstract

Numerical analysis of the transmission coefficient, local density of states, and density of states in superlattice nanostructures of cubic $$\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}$$AlxGa1-xN/GaN resonant tunneling modulation-doped field-effect transistors (MODFETs) using $$\hbox {next}{} \mathbf{nano}^{3}$$nextnano3 software and the contact block reduction method is presented. This method is a variant of non-equilibrium Green's function formalism, which has been integrated into the $$\hbox {next}\mathbf{nano}^{3}$$nextnano3 software package. Using this formalism in order to model any quantum devices and estimate their charge profiles by computing transmission coefficient, local density of states (LDOS) and density of states (DOS). This formalism can also be used to describe the quantum transport limit in ballistic devices very efficiently. In particular, we investigated the influences of the aluminum mole fraction and the thickness and width of the cubic $$\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N}$$AlxGa1-xN on the transmission coefficient. The results of this work show that, for narrow width of 5 nm and low Al mole fraction of $$x = 20\,\%$$x=20% of barrier layers, cubic $$\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}$$AlxGa1-xN/GaN superlattice nanostructures with very high density of states of 407 $$\hbox {eV}^{-1}$$eV-1 at the resonance energy are preferred to achieve the maximum transmission coefficient. We also calculated the local density of states of superlattice nanostructures of cubic $$\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}$$AlxGa1-xN/GaN to resolve the apparent contradiction between the structure and manufacturability of new-generation resonant tunneling MODFET devices for terahertz and high-power applications.