Electronic States And Light Absorption In GaN-Based Core-Shell Nanowires

Core-shell nanowires have many advantages in the application of optoelectronic devices and have attracted much attention.The core-shell heterostructure nanowires are different from the ordinary axial heterojunction one-dimensional nanomaterials,which have a long interface along the axial direction,while the charge separation occurs in a shorter radial direction,greatly reduced the recombination probability of light-induced carriers in the material and then improved the carrier transport and photoelectric conversion efficiency.Whether it is the quantum size limitation effect or the energy band change caused by the change of the conduction band gap of the two materials,the relative positions of the energy bands of the nanowire structure of the core-shell heterostructure can be adjusted,thereby broadening the spectrum response range of the new photoelectric device prepared therefrom.In this paper the influence of the composition,core radius and temperature of the core material on the conduction band gap width and effective electron mass are considered in detail.Within the effective mass approximation,numerical solution of the electronic stationary state Schrodinger equation in AlxGa1-xSN/AlN core-shell nanowires is given by finite element difference method.And the eigen-energies,the corresponding eigenwave functions and the light absorption coefficients of the electron are obtained.The calculation results show that at room temperature,when the core radius is constant,as the component x increases,the conduction band between the core and the shell decreases,the energies of the electron in the potential well decreases,the possibility of tunneling barriers for electrons increase,then the peak value of the light absorption coefficient decreases and the peak of the light absorption coefficient has a red-shift.When the composition is constant,as the core radius increases,the energies of the electron in the potential well decrease,and the possibility of tunneling barriers for electrons increases,then the peak value of the light absorption coefficient increases,and the peak of the light absorption coefficient has a red-shift,and the red-shift amplitude of each absorption peak decreases with the increasing of the core radius.When the core radius of core-shell structure nanowires is constant and the composition is fixed,,as the temperature increases,the energies of the electron in the potential well are improved,the most significant improvement is in the higher eigen-energies are improved significantly.Because with the increase of temperature,the possibility of tunneling barriers for electrons at lower energy levels do not change more.The tunneling of electron-to-barriers at higher energy levels enhances as the temperature increases significantly.With the increase of temperature,the peak value of the absorption coefficient decreases.However,at low temperatures,the peak fall is small,at high temperatures,the peak fall is larger.As the temperature rises,the peak of the light absorption coefficient has a blue-shift.The blue-shift amplitude of the light absorption peak at low temperature is small,and the blue-shift amplitude of the light absorption peak gradually increases at high temperature.When the temperature is higher,the modulation effect will become worse and the temperature modulation will lose its significance.