Analyzing the Contact-Doping Effect in In₂O₃ FETs: Unveiling the Mechanisms Behind the Threshold-Voltage Roll-Off in Oxide Semiconductor Transistors

Abstract

In this work, the contact-doping effect (CDE) and its impact on the threshold voltage ( V-T ) roll-off in indium oxide (In2O3 ) field-effect transistors (FETs) are systematically studied. By analyzing the long channel length ( L (ch )) and short L (ch )devices separately using a modified transfer length method (TLM), Delta L can be extracted to quantify the CDE. The correlation between Delta L and the L(ch )at which V (T )roll-off occurs suggests that CDE may be a key factor contributing to the V(T )roll-off in In(2)O(3 )transistors. Next, the underlying mechanisms of CDE are investigated. It is found that oxygen scavenging reactions (OSRs) during the deposition of source/drain (S/D) metals on the In( 2)O(3 )channel is one of the reasons behind CDE. S/D metals can scavenge oxygen atoms from In2 O3 , creating oxygen vacancies and increasing the carrier density near the S/D regions. Additionally, the Schottky barrier height ( Phi(SB) ) of metal/In(2 )O(3 )contacts might also influence the CDE: a positive Phi SB depletes carriers, while a negative Phi(SB) accumulates them in the In( 2 )O(3 )channel under the S/D. This study provides a new approach to investigating CDE and highlights its critical role in understanding the V(T )roll-off in oxide semiconductor (OS) transistors.