Fundamental oscillations up to 200 GHz in resonant tunneling diodes and new estimates of their maximum oscillation frequency from stationary-state tunneling theory

Abstract

Fundamental oscillations have been measured up to 200 GHz in resonant‐tunneling diodes at room temperature. Oscillations in the range 102–112 GHz were achieved with diodes mounted in a WR‐6 waveguide resonator, and the peak output power in this range was approximately 5 μW. The same diodes oscillated between 192 and 201 GHz and generated about 0.2 μW when mounted in a WR‐3 resonator. The estimated maximum oscillation frequency ( f_max) for these devices is 244 GHz, assuming the average drift velocity across the depletion layer to be 4×10⁷ cm s⁻¹. This estimate has been obtained from a new phenomenological theory of the negative differential conductance which accounts for the frequency‐dependent spreading resistance and transit‐time delay. The theory is also used to show that diodes having f_max exceeding 600 GHz are feasible simply by modifying the doping profile in the regions on either side of the double‐barrier structure.