Process and device integration for silicon tunnel FETs utilizing isoelectronic trap technology to enhance the ON current

Abstract

A tunnel FET (TFET) is a candidate replacement for conventional MOSFETs to realize low-power LSI. The most significant issue with the practical application of TFETs concerns their low tunneling current. Si is an indirect-gap material with a low band-to-band tunneling probability and is not favored for the channel. However, a new technology has recently been proposed to enhance the tunneling current in Si-TFETs by utilizing isoelectronic trap (IET) technology. IET technology provides an innovative approach to realizing low-power LSI with TFETs. In this paper, state-ofthe-art research on Si-TFETs with IET technology from the viewpoint of process and device integration is reviewed.

ON current enhancement and variability suppression in tunnel FETs by the isoelectronic trap impurity of beryllium

“…This follows the previous study. 15,38) In terms of I ON , SS, and V th variation, σ(I ON )/〈I ON 〉, σ(SS), and σ(V th ), the Be-IET TFETs exhibited 75%, 64%, and 78% smaller dispersions than the control, respectively. This indicates that it is possible to fabricate TFET integrated circuits with smaller voltage margins by introducing Be-IET as well as Al-N IET.…”

“…The variability suppression can be understood as a result of the suppression of the tunneling rate fluctuation by introducing Be-IET, according to the discussion in previous studies. 15,38) The correlation between tunneling rate fluctuations (ΔG/G) and electric field fluctuations (ΔE/E) is derived from Kane's BTBT model 39,40) as ΔG/G = SΔE/E, where S ≡ γ + B/E is the sensitivity coefficient. 15,38) Here, γ is 2 and 2.5 for direct and indirect BTBT, respectively, and B is Kane's tunneling parameter.…”

“…15,38) The correlation between tunneling rate fluctuations (ΔG/G) and electric field fluctuations (ΔE/E) is derived from Kane's BTBT model 39,40) as ΔG/G = SΔE/E, where S ≡ γ + B/E is the sensitivity coefficient. 15,38) Here, γ is 2 and 2.5 for direct and indirect BTBT, respectively, and B is Kane's tunneling parameter. Note that smaller B corresponds to higher tunneling probability.…”

Enhancement of tunneling currents by isoelectronic nitrogen-atom doping at semiconductor pn junctions; comparison of indirect and direct band-gap systems

“…[11][12][13][14] In 2014, Mori and coworkers succeeded in remarkably enhancing an ON current in Si-TFET utilizing the isoelectronic co-doping of Al and N atoms around the pn junction. [15][16][17][18][19][20][21] In order to clarify the electronic structures of such codoping systems, our group showed by the first-principles calculation that Al and N atoms produce a nearest-neighboring pair in Si layers and produce an electron-unoccupied isoelectronic impurity state below the conduction-band of Si. [22][23][24] In addition, by using the one-dimensional model and wave-packet simulation, 25,26) we showed that such an impurity state becomes the resonance state with conductionband states of n-Si layers when the Al-N pair is located in Si-pn junction under the electric field, shortens the tunneling length between p-and n-Si layers as a stepping stone, and markedly increases the tunneling current, which well explains the experiments.…”

“…© 2022 The Japan Society of Applied Physics n m of host bulk semiconductors of Si, Ge, GaP, InP, and GaAs are taken from previous literatures. [28][29][30][31][32] As isoelectronic N-atom dopants, we consider an Al-N nearest-neighboring pair in Si and Ge, [15][16][17][18][19][20][21][22][23][24] and an isolated N atom in GaP, InP, and GaAs. We assume that these impurity atoms are substitutionally located at atomic sites of host semiconductors, especially at anion site in GaP, InP, and GaAs.…”