Large-signal model for a Resonant Heterojunction Tunnelling Transistor RTD(n)-p-n

A large-signal model is presented for a Resonant Tunnelling Bipolar Transistor (RTBT) with a double barrier structure at the Emitter. These devices show large collector current peak-to-valley ratios (PVR) in the common-emitter transistor configuration because of significant current gain reduction beyond resonance. This large PVR makes them attractive devices for circuit applications, including high speed analog-to-digital converters. The model combines the Current-Voltage relationship for a Heterojunction Bipolar Transistor (HBT) and the Current-Voltage relationship for a Resonant Tunnelling Diode (RTD). The thermionic emission effects along the structure, across the RTD's barriers and across the HBT's heterojunction are taken into account. The HBT model is based on the extended Gummel and Poon model of Parikh and Lindholm which takes into account the current flow across the emitter-base and the base-collector heterojunctions. The RTD is modelled in the coherent tunnelling regime and incorporates thermionic effect regime. Model results are presented for a 3 μm×3 μm device published in the literature - an InGaAs/AlAs on InP resonant tunnelling heterojunction bipolar transistors.