Influence of n⁺-layer-gate gap on short-channel effects of GaAs self-aligned MESFET's (SAINT)

Abstract

Short-channel effects of GaAs n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -gate self-aligned MESFET's are investigated for different n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -layer-gate gaps. The gate lengths range from 0.1 to 1.5 µm. The fabrication features are self-aligned implantation for n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -layer technology (SAINT) and an electron-beam direct writing. The n+-layer-gate gap is controlled by the undercut process in the bottom resist of a multilayer resist acting as n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ion implantation mask. It is shown that the short-channel effects such as an increase in subthreshold current and a negative shift of threshold voltage can be substantially alleviated by enlarging the n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -layer-gate gap from 0.15 to 0.3 µm.