Switching time measurements of GaAs/AlAs and InGaAs/AlAs resonant tunnelling diodes

Resonant tunnelling diodes (RTDs) have attracted much interest because of their potential use for high frequency and high speed applications. An important study of RTDs is therefore to analyse the high speed switching time between stable states of a device. The rise time calculation technique described by Diamond et al. for simple pulse-forming circuits has been used to measure the high speed switching response of our RTDs. Two types of RTDs-GaAs/AlAs on GaAs, with alloyed GaAs(n/sup +/)ohmic contacts, and InGaAs/AlAs on InP, with non-alloyed InAs(n/sup +/)ohmic contacts were designed, fabricated, modelled and measured, With a peak current density of 20 kA/cm/sup 2/ and a Peak-to-Valley Ratio (PVR) of 4:1, the GaAs/AlAs RTD switching time is 20 ps. With a peak current density of 48 kA/cm/sup 2/ and PVR of 2:1, the InGaAs/AlAs RTD switching time is less than 5 ps, the limit of resolution of our measurement equipment. When compared with GaAs/AlAs RTDs, the In/sub 0.53/Ga/sub 0.47/As/AlAs material shows superior switching time performance. Our results are comparable to the best devices reported and are well suited for ultra-fast switching applications.