Tunable-Frequency Gunn Diodes Fabricated by Focused Ion-Beam Implantation.

We report the fabrication of planar Gunn-effect diodes in which the fundamental transit-time mode oscillation frequency can be tuned over a wide range by varying the dc bias across the device. The tunability is due to a linear doping concentration gradient between the contacts. This lateral doping profile was created by implanting GaAs with a focused beam of silicon ions and smoothly increasing the dose from contact to contact. For a device with a ramp length of 3 mum, a frequency tuning range from 19 to 41 GHz was achieved, the widest band exhibited to date by a single Gunn oscillator. A transient-energy model based on a solution of the Boltzmann transport equation is used to study domain propagation in graded material and to predict doping profiles which optimize device performance. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.).