Influence of Asymmetric Spacer Layers on Resonant Tunneling Diodes

Resonant Tunneling Diodes (RTD) is one of the most promising candidates for room temperature terahertz oscillators. In order to increase the upper limit of radiation frequency in RTD terahertz oscillators, peak voltage must be decreased to suppress Г to L transition. In this work, RTDs with asymmetric spacer layers has been investigated using SILVACO-ATLAS software. We demonstrated that peak voltage could be decreased effectively by decrease the emitter-to-collector spacer thickness ratio. A qualitative theory regarding electron concentration discrepancy has been proposed to explain the decrease in peak voltage, based on simulation results conducted by SILVACO-ATLAS. The presence of a build-in electrical field in the double barrier region (DBR) due to the electron concentration discrepancy between two sides of DBR is demonstrated, resulting in a reduction of the ground state energy level and subsequently leading to a decrease in peak voltage. This work presents that it is a simple but effective approach to optimize RTD oscillators by adjusting the emitter-to-collector spacer thickness ratio.