Impact of Floating Body Effect, Back-Gate Traps, and Trap-Assisted Tunneling on Scaled In0.53Ga0.47As Ultrathin-Body MOSFETs and Mitigation Measures

Abstract

Ultrathin-body (UTB) III–V channel MOSFETs are known to suffer from the floating body effect which turns on a parasitic bipolar junction transistor (BJT) and increases the off-state leakage current. This paper presents a TCAD simulation study of UTB In0.53Ga0.47As n-channel MOSFETs with nanowire and planar device geometry, each with different gate lengths ( ${L}_{G}$ ) ranging from 13 to 300 nm. A single set of parameters results in good agreement with measured transfer characteristics of all six different device geometries. The impact of band-to-band tunneling (BTBT), trap-assisted tunneling (TAT), and the electrostatic effect of traps at the buried-Al2O3/InGaAs interface has been deconvoluted during the TCAD analysis. It is found that the turn-on of the parasitic BJT is mainly caused by the combined effect of BTBT at the channel–drain junction and TAT at the gate-oxide/drain overlap. Furthermore, it is revealed that traps at the buried-Al2O3/InGaAs act as a backgate and degrade the subthreshold swing of the planar MOSFETs. The off-state leakage due to the parasitic BJT could be minimized with the help of an oxide spacer between HfO2 and InGaAs drain and by introducing a dopant grading at the source–channel and the drain–channel interfaces.