Bias-Dependent Spectrum Analysis of Highly Nonlinear Resonant Tunneling Diode Oscillators

Many resonant tunneling diode (RTD) devices employ antenna structures that emit signals towards the backside of the substrate exhibiting high permittivity. Consequently, these devices are prone to coupling into substrate modes. The intended increased nonlinearity of optimized RTDs results in an amplified susceptibility of the oscillator to coupling phenomena with resonant substrate modes. We present small area devices with reduced capacitance that are integrated into antennas with high inductance. This design allows for the creation of highly nonlinear oscillators and enables the investigation of the spectral performance under varying bias conditions. The measurements indicate the occurence of spurious oscillations which are estimated to be multiples of resonant substrate modes in the extended device structure.