Harmonic distortion analysis of short channel junctionless nanowire transistors operating as amplifiers

Abstract

The increasing demand for Systems-on-Chip, where digital and analog circuits coexist, drives the necessity of studying the analog properties of ultimate devices. For technological nodes below 22 nm, multi-gate architecture is considered one of the most promisors since the presence of more than one gate improves the gate control on the depletion charge making this kind of structure extremely robust to short channel effects [1]. However, due to the reduced dimensions, ultimate inversion mode (IM) multigate transistors such as triple gate or FinFETs require ultra-sharp p-n junctions between source/drain and channel. The formation of such sharp junctions is challenging as thermal and doping conditions must be carefully controlled. For this reason, a novel accumulation-like multigate structure, so-called Junctionless Nanowire Transistor (JNT) was recently developed [2-3]. This structure presents no p-n junctions since it consists of a silicon nanowire surrounded by gate stack and heavily doped with the same impurity type (n-type for nMOS devices and p-type for pMOS ones) and concentration from source to drain. For gate voltages (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</inf> ) above the threshold (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> ), the current flows primarily due to bulk conduction whereas at low gate voltages the silicon layer becomes fully depleted, turning off the transistor [4]. JNTs have shown better DIBL, subthreshold slope and analog properties than IM multi-gate transistors of similar dimensions [5,6]. Also, long channel n-type JNTs have shown lower harmonic distortion (HD) than triple gate FinFETs of similar dimensions [7]. This paper evaluates, for the first time, the non-linearity of short channel p-and n-types JNTs operating in saturation as single transistor amplifiers. The influences of the intrinsic voltage gain (A <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</inf> ), the temperature (T) and the doping concentration on HD are observed.