Numerical Study Of Ferromagnetism In Ⅲ-Ⅴ Diluted Magnetic Semiconductor

In this work, we have concerned with the Curie temperature (T_c) of Mn selectively 8 -doped asymmetry double quantum wells heterostructures. The aim of our work is to obtain a complete understanding between the magnetic properties and the condition of Mn dopants for the structure.Firstly we presented a self-consistent analysis of the T_c modulation in Mn δ -doped GaAs/Be-doped AlGaAs heterostructures. Considering both the influences of Mn dopants and Hartree potential, we solve simultaneously the SchrOdinger and Poisson equations for different Mn δ -doping positions (d_s) and effective Mn dopants concentration (N_Mn). Under low hole concentration (N_Mn≤4e15/m²), the peak position of the two dimensional hole gas (2DHG) envelope function is independent on δ-doping position and fixed at the 4nm distance away from the heterointerface. Further increasing the hole concentration under low temperature annealing will lead to the remarkable shift of the envelope function. T_c of the heterostructure can be enhanced up to 1.6 times under optimized calculational parameters.We use the successful method in studying GaAs/AlGaAs heterostructures to do the same research in GaN/AlGaN quantum wells. Transfer matrix method has been used to analyze T_c modulation by polarization-induced built-in electric fields in Mn δ -doped GaN/AlGaN quantum wells. SchrOdinger equation is employed to calculate the quantum-confined subband energies and the distribution of their corresponding envelope functions. Based on these, we investigate the dependence of T_c on the built-in electric fields in different structures of quantum well. By changing the asymmetry of double quantum wells (DQW), T_c can be enhanced up to 3 times.At last,starting from the mean-field theory of carrier-induced ferromagnetism in III-V DMS along with the exchange-correlation interaction of holes within the local spin density approximation, we found that the T_c of DMS quantum-wells exhibits step-function-like dependence on the hole density, which is interpreted to Be caused by the quasi-two-dimensional nature of systems. Moreover, the temperature dependence of the spin polarization shows quite distinct characteristics depending on the hole density.