Propriedades eletrônicas e processos ópticos lineares de nanofios quânticos semicondutores com heteroestruturas axiais

Abstract

Heterostructured semiconductor nanowires are potential candidates for application in nanoelectronics and photonic devices, due to their important electronic and optical properties, which arise from the conditions imposed by two degrees of confinement, such as transistors, light-emitting diodes, nanoscale lasers, and devices thermoelectrics. In this work, we investigate the electronic properties and linear optical processes of AlxGa1−xAs/GaAs quantum wells axially patterned in cylindrical nanowires, the so-called axial quantum wires. We study the effects produced in linear optical processes, which arise due to changes in the electronic properties of electrons and holes when parameters such as the Aluminum molar fraction x, nanowire radius r, and quantum well width L are adjusted. It is well known that the band alignment in AlxGa1−xAs/GaAs quantum wells can be switched between type I alignment and type II alignment through changes in the value of the molar fraction x. We show that, in addition to the molar fraction x, the band alignment can also be adjusted from type I to type II by changes in the value of the quantum wire radius r. The theoretical framework is based on the numerical solution of the Schrödinger equation in cylindrical coordinates, which is consistent with the effective mass approximation and the mathematical formalism of the envelope function. Linear optical processes are described based on the calculation of first-order optical susceptibility, which is obtained from the density matrix theory in quantum mechanics. An axially patterned quantum well in a nanowire presents three degrees of confinement of its carriers, and in this work, our results contribute to demonstrating how the gap engineering of this system is carried out through the control of its parameters. Thus, we show how the exciton recombination energy is affected, and consequently, we describe the changes in linear optical properties, such as optical absorption coefficient and refractive index.