Modeling and characteristics of bistable optoelectronic switches and heterojunction field effect transistors in molecular-beam epitaxially grown SiGe/Si

Abstract

Recent progress in experimentally realizing, characterizing, and modeling bistable digital optoelectronic switches (DOES) and heterojunction field effect transistors (HFETs) is presented in this communication. Using a computer-based model, the design of the molecular-beam epitaxially grown Si/SiGe heterostructure is shown to affect a number of operational parameters in both the DOES and the HFET. For the DOES, these parameters include the switching voltage Vs and the sensitivity of the device to injected current via a third terminal. For the HFET, the threshold voltage Vth and gate leakage are both shown to be affected by heterostructure design. Experimentally, the sensitivity of Vs to third terminal input which modulates the hole population at the heterointerface is compared to that for a contact made to the active region. In addition, the observation of steplike transitions in the source-drain current–voltage characteristics for a range of gate voltages is reported for HFETs. These transitions are explained as feedback in the transistor structure and are related to the feedback in the DOES. These electrical characteristics form the basis for a new inversion-channel device designated, the bistable field effect transistor.