50 GHz resonant tunneling diode relaxation oscillator

InAlAs/AlAs based RTDs with a peak current density over 500 kA/cm² have been designed and fabricated. Relaxation oscillator circuits for 20 and 50 GHz were designed using these 0.6 μm² RTDs. They consist of an RTD and a 5 Ω resistor placed in a coplanar waveguide (CPW). The measured spectrum of the 20 GHz and 50 GHz oscillators showed only odd harmonics. The measured results of the relaxation oscillators show that they have very low phase noise (low jitter), below -110 dBc/Hz at 1 MHz offset in locked-mode, and can easily be phase locked. RTD based relaxation oscillation can be readily used as clocks in high-speed signal processing applications.