Horizontal Current Bipolar Transistor DC Performance at Cryogenic Temperatures

Abstract

The DC current gain ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta {)}$ </tex-math></inline-formula> of Si bipolar junction transistors (BJTs) reported so far decreases at cryogenic temperatures (CT), or shows a very limited improvement at best. For temperatures above 90 K, the Horizontal Current Bipolar Transistor (HCBT) behaves comparably to other published Si BJTs. However, cryogenic measurements of HCBT devices show a steep <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> increase at temperatures below 90 K. We report a current gain of 85 at 300 K, a minimum <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> of 31 at 90 K and an increase of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> to 66 at 17 K. The collector-emitter breakdown voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\textit {BV}}_{\textit {CEO}}{)}$ </tex-math></inline-formula> measured around the peak <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> varies only within 0.2 V over the examined temperature range. Additionally, the Early voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{A}{)}$ </tex-math></inline-formula> increases for temperatures below 50 K, improving the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta {V}_{A}$ </tex-math></inline-formula> product at 20 K by 2.2x as compared to 300 K, which makes the HCBT a potentially attractive technology for deep cryogenic applications. TCAD simulations of an equivalent Si BJT structure show that such considerable increase of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> at CT can be attributed to the interplay between incomplete ionization (II) of acceptors in the base and bandgap narrowing (BGN) in the emitter in a specific range of HCBT doping profiles.