Effects of Bilayer Conduction on Hysteresis Characteristics of Si/SiGe Heterostructure Field-Effect Transistors at Cryogenic Temperatures
Journal
IEEE Transactions on Electron Devices
Journal Volume
73
Journal Issue
5
Start Page
2915
End Page
2920
ISSN
0018-9383
1557-9646
Date Issued
2026-04-01
Author(s)
Abstract
We investigate the bilayer conduction in undoped Si/SiGe heterostructure field-effect transistors (FETs) and its effects on hysteresis characteristics at temperatures from 300 to 1.8 K. We found that both the transconductance and first-plateau current of the devices slightly change with the channel length due to the large series resistance at cryogenic temperatures. By modulating the maximum gate bias, we find that the threshold voltage of the devices for forward sweeps stays constant, while for backward sweeps, it increases with the maximum gate bias with two distinct regimes, which can be explained by the presence of the bilayer conduction in the Si cap and quantum well (QW) layers. We also characterize forward-sweep and backward-sweep subthreshold swing (SS) at different temperatures. Both forward-sweep and backward-sweep SS saturate at deep cryogenic temperatures due to finite band-tail states. The backward-sweep SS is better at temperatures between 200 and 70 K due to the effective screening of the defects at the oxide interface by electrons tunneling from the buried Si QW.
Subjects
Field-effect transistors (FETs)
Si/SiGe heterostructure
subthreshold swing (SS)
threshold voltage (Vth)
Publisher
Institute of Electrical and Electronics Engineers (IEEE)
Type
journal article