Resonant tunneling device with multiple negative differential resistance: Digital and signal processing applications with reduced circuit complexity

A new approach to obtain multiple peaks in the current-voltage characteristic of a resonant-tunneling (RT) device is demonstrated. The peaks are generated using only the ground state resonance of the quantum well rather than several states, as in conventional RT devices. The separation between the peaks is voltage tunable and also the peak currents can be made nearly equal, which is necessary to use the device in a variety of circuit applications. A functional device operating at 100 K, with two peaks in the I-V has been fabricated. The first practical demonstration of circuits for frequency multiplication by a factor of five, a three-state memory and a 4-bit parity generator, using a single functional RT device each, is also reported. The use of multiple-peak RT devices in these circuits results in an order of magnitude reduction in the number component per function over conventional techniques.