Electron States And Light Absorption In Rectangular GaAs/AlGaAs Core Shell Nanowires

Semiconductor nanowires with strong quantum confinement and large surface area show advantages in improving integration level of electronic devices and photoelectric transforming efficiency.GaAs/Al_xGa_1-xAs heterostructure which can be used to realize the mid and far infrared radiation and absorption by electronic transition between intersubbands in conduction band,is a main system for lasers and detectors in this band.The enhanced exciton lifetime and fast photoelectric response make GaAs/Al_xGa_1-xAs core-shell nanowires?CSNWs?a promising candidate for next-generation optoelectronic devices.The stable zincblend phase of GaAs based III-V compound make it possible to prepare rectangular nanowires with high quality.In this paper,electron states and light absorption in rectangular prismatic GaAs/Al_xGa_1-xAs CSNW is investigated.Firstly,finite element difference method based on the effective mass approximation is applied to solve the two-dimensional schr?dinger equation.The electronic states in GaAs/Al_xGa_1-xAs CSNW with square and rectangle section are compared,and the variation of electronic eigen level and wave function versus size and Al component are discussed.The main conclusions are as follows:1?In the CSNW with square section,there are two degenerate states of electron on the first excited level due to the symmetry of the system.In the case with rectangular section,the symmetry breaking in xy-plane leads to elimination of the degeneracy.2?In the CSNW with square and rectangular sections,increase of core and shell thickness with fixed ration,or the separate increase of core or shell thickness,electronic eigen energy levels and level spacing,as well as the peak of wave function all decrease.When the size of CSNW is fixed,increase of Al component results in the enhancement of electron energy level,but the reduction of energy level spacing at the same time,due to the strong confinement of one-dimensional system.Furthermore,optical absorption coefficients of electronic transition between intersubbands in the system with the adjustment from core-shell size and Al component,are investigated according to the golden Fermi rule.Here are the results:3?In the CSNW with square sections,increase of core and shell thickness with fixed ration,or the separate increase of core or shell thickness,both transition matrix and level spacing between ground to the first excited states decrease.As a result,the first-order linear and third-order nonlinear as well as total light absorption coefficients all decrease with a red shift of absorption.4?When the Al composition components of shell increases while the size of the system is fixed,the first-order linear and third-order nonlinear as well as and total optical absorption coefficients of electronic transition between ground state to the first excited state all increase.However,there is a red shift of the light absorption due to the decrease of energy level spacing.This work is expected to be helpful for designing GaAs/Al_xGa_1-xAs CSNW optoelectronic devices.