Negative differential conductance in GaAs/AlAs superlattices

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Abstract
Voltage-controlled superlattice negative differential conductance (NDC) is observed in microwave impedance measurements of n-type GaAs/AlAs superlattices biased perpendicular to the layers. The electron transit time deduced from the peak NDC frequency is in good agreement with the velocity-field relation obtained from dc current-voltage measurements. The data also yield the criterions for the existence of dc or high-frequency NDC. Finally, a fine structure in the conductance-voltage data at low temperatures is interpreted in terms of inhibited perpendicular transport and high-field domain formation beyond the critical field.