Abstract: A photoconductive switch that uses materials that support negative differential mobility, whose operation leverages the pulse compression of a charge could to generate the “on” time of the pulse in combination with the speed of light to generate the “off” time of the pulse, is described. In one example, a method of operating a photoconductive switch, which includes two electrodes and a light absorbing material positioned therebetween, includes selecting a value for one or more parameters comprising a voltage for generation of an electric field, a spot size of a laser pulse, a temporal pulse width of the laser pulse, or an intensity of the laser pulse, wherein the selected value(s) for the one or more parameters enable the switch to operate in a region where the light absorbing material exhibits negative differential mobility, and illuminating the light absorbing material with the laser pulse to generate a charge cloud within the light absorbing material.

Abstract: A high electron mobility transistor (HEMT) for high frequency applications comprises: a source and a drain spaced apart on a substrate, each of the source and drain extending vertically away from the substrate; a stack of nanowire or nanosheet heterostructures suspended between the source and the drain and being vertically separated from each other, each of the nanowire or nanosheet heterostructures comprising a channel layer between top and bottom barrier layers; a gate dielectric layer on each nanowire or nanosheet heterostructure; and a gate electrode on each gate dielectric layer. Each of the channel layers comprises a first group III nitride including aluminum, and each of the top and bottom barrier layers comprises a second group III nitride including a higher amount of aluminum than the first group III nitride. The stack includes N of the nanowire or nanosheet heterostructures, where N is an integer from 2 to 50.

Abstract: A photoconductive switch that uses materials that support negative differential mobility, whose operation leverages the pulse compression of a charge could to generate the “on” time of the pulse in combination with the speed of light to generate the “off” time of the pulse, is described. In one example, a method of operating a photoconductive switch, which includes two electrodes and a light absorbing material positioned therebetween, includes selecting a value for one or more parameters comprising a voltage for generation of an electric field, a spot size of a laser pulse, a temporal pulse width of the laser pulse, or an intensity of the laser pulse, wherein the selected value(s) for the one or more parameters enable the switch to operate in a region where the light absorbing material exhibits negative differential mobility, and illuminating the light absorbing material with the laser pulse to generate a charge cloud within the light absorbing material.