Discrete current steps and period-adding bifurcations observed in an ac-driven GaAs/AlAs semiconductor superlattice
The nonlinear vertical transport properties of an ac-driven GaAs/AlAs superlattice have been studied in dynamic voltage bands (DVBs). With the dc bias as a control parameter, period-adding bifurcations are observed within DVBs and the measured time-averaged currents exhibit a series of discrete current steps. At each bifurcation point, the change of discrete current is proportional to the change of locking frequency. These phenomena can be understood in terms of the novel waveforms of the temporal current recorded on the current steps.