ABSTRACT: This thesis presents experimental results and theoretical analysis of the dynamical behavior of a series array of tunnel diodes with each element connected in parallel with a capacitor. Previous work has studied the theoretical behavior of such a series array using ideal negative differential resistance (NDR) circuit elements to model the tunnel diodes and found that heterogeneity and applied bias voltage ramp rate are key to the formation of current branches. Such models can provide key insights into the behavior of more complex NDR semiconductor devices, such as semiconductor superlattices and quantum cascade lasers. Tunnel diodes and arrays thereof are also interesting in their own right due to their applications in microwave frequency electronics. In this work we expand upon the previous work by first experimentally measuring the behavior of an array with a single tunnel diode element, and then experimentally checking the predicted dynamics for 8 tunnel diode elements. We notice certain discrepancies in the produced current branches between the numerical and experimental results and seek to explain them by including parasitic reactance elements in the model for each NDR element. We find that adding these additional reactance elements produces a distinct structure for the effective intrinsic current-voltage (I − V ) curve of the NDR elements, which modifies the current branches produced by the array of N elements to a form qualitatively similar to that observed experimentally. We analyze the voltage distribution across each element of the array as a function of the bias voltage ramp time and note how this distribution relates to the evolution of the I −V curve for the entire array. We then use this connection to define a field inhomogeneity parameter which succinctly describes the evolution of the array field distribution and I − V curve across the range of bias voltage ramp times. We also examine how shot noise in the system affects the array transitions across current branches and find qualitatively similar results to those seen previously in semiconductor superlattices for the evolution of the stochastic distribution of the transition time for different bias voltages. Finally, we introduce the use of the averaging method into the theoretical analysis, which allows us to retain the more accurate results of the new model while keeping the dynamical simplicity of the original model by replacing the nonlinear intrinsic I − V curve of an individual tunnel diode by an appropriately time-averaged form.
Here is the complete thesis in PDF: Brown Thesis