Microwave characterization of the contiguous domain oscillator

The authors report the first observation of microwave oscillation in the contiguous domain oscillator (CDO). Computer simulations indicate that, if the channel field V/sub GG//L is in the regime of negative differential mobility for electrons in GaAs, a contiguous sequence of charge domains will form spontaneously along the entire length of the channel, continuously drifting into the drain. Experimental devices were fabricated using a standard ion-implanted MESFET process, modified to include a WSiN resistive gate. The gate resistivity is 30 k Omega /sq, channel doping is 1.2*10/sup 17/ cm/sup -3/, and channel thickness is 150 nm. Channel widths range from 200 to 400 mu m and lengths from 10 to 50 mu m. Devices were mounted in a waveguide insertion unit, and operation was characterized between 26 and 140 GHz using a Tektronix 2755P spectrum analyzer. Modulation of the oscillation frequency by the gate-to-source V/sub G1-s/ was observed, as predicted by the computer simulation.