The wideband tunability of double Gunn diodes

Abstract

Gunn diodes use the Ridley–Watkins–Hilsum effect to generate low noise millimeter wave signals for communication and sensing applications. However, Monte Carlo calculations indicate that the velocity–field characteristics of compensated GaAs contain a second peak due to phonon scattering. A novel device that leverages this double Ridley–Watkins–Hilsum effect to achieve ultra-wideband tunability of low-noise millimeter waves is proposed in this article. The second region of negative differential mobility is gradually introduced in seven mobility profiles, which are each simulated in eight device lengths. It is found that a 2.5 μm Gunn diode with a compensation ratio of 0.6 operating at 160 K has a 700% increase in frequency tunability. An analysis of the domain formation indicates that the increase in tunability is due to significant distortions in domain shape. Gunn diodes with transit lengths of 2 μm and smaller show a 100% increase in tunability due to modulations in the effective transit length and absorption rate. These simulations indicate that compensated GaAs could provide linear, ultra-wideband frequency tunability.