Analog/RF Performance of Triple Material Gate Stack-Graded Channel Double Gate-Junctionless Strained-Silicon MOSFET with Fixed Charges

In this paper, analog/radio frequency (RF) electrical characteristics of triple material gate stackgraded channel double gate-Junctionless (TMGS-GCDGJL) strained-Si (s-Si) MOSFET with fixed charge density is analyzed with the help of Sentaurus TCAD. By varying the various device parameters, the analog/RF performance of the proposed TMGS-GCDG-JL s-Si MOSFET is evaluated in terms of transconductance-generationfactor (TGF), early voltage, voltage gain, unity-powergain frequency ( f max ), unity-current-gain frequency ( f t ), and gain-transconductance frequency product (GTFP). The results confirm that the proposed TMGS-GCDGJL s-Si MOSFET has superior analog/RF performance compared to gate stack-graded channel double gatejunctionless (GS-GCDG-JL) s-Si device. However, the proposed MOSFET has less transconductance and less output conductance when compared with the GS-GCDGJL s-Si device in above threshold region, and reverse trend follows in sub-threshold region.

Electron–hole superfluidity in strained Si/Ge type II heterojunctions

Excitons are promising candidates for generating superfluidity and Bose–Einstein condensation (BEC) in solid-state devices, but an enabling material platform with in-built band structure advantages and scaling compatibility with industrial semiconductor technology is lacking. Here we predict that spatially indirect excitons in a lattice-matched strained Si/Ge bilayer embedded into a germanium-rich SiGe crystal would lead to observable mass-imbalanced electron–hole superfluidity and BEC. Holes would be confined in a compressively strained Ge quantum well and electrons in a lattice-matched tensile strained Si quantum well. We envision a device architecture that does not require an insulating barrier at the Si/Ge interface, since this interface offers a type II band alignment. Thus the electrons and holes can be kept very close but strictly separate, strengthening the electron–hole pairing attraction while preventing fast electron–hole recombination. The band alignment also allows a one-step procedure for making independent contacts to the electron and hole layers, overcoming a significant obstacle to device fabrication. We predict superfluidity at experimentally accessible temperatures of a few Kelvin and carrier densities up to ~6 × 1010 cm−2, while the large imbalance of the electron and hole effective masses can lead to exotic superfluid phases.