Cyclotron emission from quantized Hall devices: Injection of nonequilibrium electrons from contacts

Emissions of cyclotron radiation associated with the inter-landau-level tra nsition of nonequilibrium electrons are experimentally studied in quantum-H all-effect devices. It is confirmed that both the longitudinal resistance a nd the contact resistance an vanishing when the cyclotron emission (CE) is being observed. For the CE, a critical source-drain voltage V-SD is found t o exist at V-SD = h omega(c)/2e, where h omega(c) is the inter-landau-level energy spacing. Spatially resolved measurements reveal that the CE takes p lace at both of the current entry and exit corners ("hot spots") of the Hal l bars, A model of ideal current contacts is discussed. The CE on the sourc e side is interpreted as being due to injection of nonequilibrium electrons from the source contact, and the CE on the drain side as due to an inter-l andau-level electron tunneling caused by a steep potential wall formed at t he drain contact. [S0163-1829(99)04619-6].