Optimize The Simulation Of Vertical Transport In Doped GaAs/AlAs Superlattice With Weak Coupling

The electric field domains and current self-oscillations which result from sequential resonant tunneling between different subbands of the superlattice are very significant phenomena.We have optimized the simulation using Matlab software. Comparing the processing data ,we know that various ode commands solve problems with different difficulties. For problems of vertical transport in the superlattice at fixed d.c. bias voltage, ode45 is optional. For problems of vertical transport in the superlattice with the increasing bias voltage and the relatively higher doped densities, ode15s is optional.The mechanisms of the electric field domain and current self-oscillations in doped GaAs/AlAs superlattice with weak coupling have been investigated by simulations. When the applied bias voltage is changed within positive slope regions of U-I curve, the domain boundary between the high and low electric field domains does not moved, and the size of electric field domains regions is also not altered, while the electric field strengths are adjusted. However, when the applied bias voltage is located within negative slope regions of U-I curve, the superlattice will undergo a very fast dynamic process, changing from one stable state to another stable state. The superlattice exhibits temporal current oscillations in the negative differential conductivity region at fixed d.c. bias voltage, which are related to the superlattice structural paraments, the doped densities and the applied bias voltage.We have also investigated the characteristics of superlattice under hydrostatic pressure by simulations. For the first current plateau, two kinds of sequential resonant tunneling of Γ-Γ process and Γ-X process are observed in the wide barrier GaAs/AlAs superlattice under various pressures．For p<2kbar,the high－field domain is formed by Γ-Γ process,while for p>2kbar,the high－field domain is formed by Γ-X process．When the barrier width was decreased to 2nm, we found that ground-state Γ-Γresonant peak was obviously higher than that of the ground-state Γ-X resonant, so that the transport in the high field domain was still controlled by Γ-Γ resonant under higher pressure.The calculated results above is nearly consistent with the experimental data.