Fabrication of Nanoscale Microwave Detectors and Generators Based on the Ratchet Effect - T.J. Beck
From Katie Gentilello
Microwave radiation induced photovoltage in two-dimensional electron gas (2DEG) materials is a promising system for supporting carrier transport without the need for an externally applied bias. Typically these systems produce photovoltages in the nanovolt range, however it has been demonstrated that it is possible to enhance the photovoltage by taking advantage of the ratchet effect. We use the ratchet effect to produce current generating and detecting devices in a Si/SiGe heterostructure. To create a ratchet effect in our chosen material we use an asymmetrical scattering mechanism. The asymmetrical pattern acts as a preferential scatterer directing transport of the carriers in one direction resulting in a potential difference. In order to maximize the efficiency of the microwave irradiation the spacing of our asymmetrical pattern was carefully chosen to coincide with the mean free path of an electron. Beginning with a typical Hall Bar structure laid down on our Si/SiGe heterostructure we pattern an asymmetrical array within the Hall Bar using Electron Beam Lithography. This array is then transferred via plasma etch into the 2DEG material and the resulting system is exposed to microwave radiation. It is found that upon irradiation of our samples a potential difference can be measured across the Hall Bar Structure. These microwave devices have great potential for use in communication devices and wireless technology.