Frequency Increase of Resonant Tunneling Diode Oscillators in Sub-THz and THz Range Using Thick Spacer Layers

Abstract

We obtained frequency increase of resonant tunneling diode (RTD) oscillators using thick spacer layers at the collector in sub-terahertz range. This is attributed to reduction of parasitic capacitance due to the increase of spacer layer thickness. The oscillation frequency increased from 325 to 425 GHz by the change of spacer layer thickness from 5 to 45 nm in reasonable agreement with theoretical calculation. Frequency switching with bias direction was also obtained for an RTD having an asymmetric structure with the thickness of the collector and emitter spacer layers of 30 and 5 nm, respectively. The oscillation frequency was 394 GHz under forward bias, whereas 336 GHz under reverse bias in which the role of the emitter and collector spacers was exchanged.