Abstract: A transferred electron effect device (1) has adjacent its cathode contact region (3) an injection zone (60) defining a potential barrier (P) for causing electrons to be emitted, under the influence of an electric field applied between the cathode and anode contact regions (3 and 4), into the active region (5) of the device with an energy comparable to that of a relatively high mass, low mobility satellite minimum (L) of the active region (5). The anode contact region (4), active region (5), injection zone (60) and cathode contact region (3) are grown sequentially, for example using molecular beam epitaxy, on a substrate which is then selectively removed to expose the anode contact region. A heat sink (70) is provided in thermal contact with the anode contact region (4). Providing the heat sink (70) in thermal contact with the anode contact region (4) rather than the cathode contact region (3) enables a significant increase in rf output power.

Abstract: In a microwave oscillator device, wires (1,2,3 etc) form inductors in a feedback path between a control electrode (e.g. gate) and a second main electrode (e.g. source) of a transistor (e.g. a GaAs MESFET). The transistor body (10) is mounted within an insulating surround 25, on a base 21 providing a first device terminal. The connection to the second main electrode comprises in series at least first and second lengths (1,2) of wire, whereas the connection to the control electrode comprises a third length (3) of wire. The invention permits the construction of a mechanical and electrical replacement for a Gunn diode by compressing the wire lengths (1,2,3 etc) in a particular arrangement into the small space inside a conventional Gunn diode envelope (20).