Limit cycle oscillation in negative differential resistance devices

We present experimental current-voltage curves for GaAs/AlGaAs resonant tunneling diodes which show complicated multiple step structures when biased into negative differential resistance. We show that these results can be explained as limit cycle oscillations in the nonlinear dynamical system consisting of a negative differential resistance device loaded with a resonant circuit. Two circuit models, a resistor-capacitor-inductor load, and the dispersionless transmission-line load, are discussed. The limit cycles in the second model exhibit a variety of behaviors characteristic of nonlinear systems, such as bifurcations, period doubling, and Devil’s Staircases, resulting in good qualitative agreement with experiment.