Analysis of Multivalley Phenomena in InP/GaAsSb DHBTs Using the Boltzmann Transport Equation

Electron transport in an indium phosphide (InP)/GaAsSb double heterojunction bipolar transistor (DHBT) is investigated by means of self-consistent Boltzmann transport equation (BTE) simulations. For this purpose, the doping profile and material parameters were calibrated to measurement data of a reference technology, leading to very good agreement between simulated and measured terminal characteristics. A rigorous analysis of the transit time components reveals a dominant role of base (τ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>mB</i></sub>) and BC depletion region transit time (τ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>BCi</i></sub>). It is shown that intervalley transfer (ivt) between <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Gv$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Lv$</tex-math></inline-formula> valley significantly increases τ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>mB</i></sub>, a useful insight for future technology optimization. Small-signal analysis is leveraged to understand the fundamental high-frequency limitations of the technology.