Responsivity Enhancement of Wafer‐Bonded In0.53Ga0.47As Photo‐Field‐Effect Transistor on Si Substrate via Equivalent Oxide Thickness Scaling

A high‐responsivity photo‐field‐effect transistor (photo‐FET) with a metal‐oxide‐semiconductor (MOS) structure is a promising technology for low‐intensity light detection with its high gain and low operation voltage. To enhance their responsivity, the equivalent oxide thickness (EOT) scaling is one of the effective solutions, which is a common technology to improve the electrical properties of MOSFETs using higher‐k insulators. Herein, the EOT scaling effect on the optoelectrical characteristics of photo‐FETs using Al2O3 and Al2O3/HfO2 gate stacks is investigated. Thanks to the EOT scaling effect introducing Al2O3/HfO2, only the transconductance of the photo‐FET is enhanced without any significant change in the photovoltaic effect and cavity effect. As a result, its responsivity is improved by up to 1.7 times. The results give a basic strategy of the EOT scaling effect for photo‐FETs; thus, the EOT scaling with a higher‐k insulator is a powerful solution for the high‐performance InGaAs photo‐FET requiring high responsivity in the short‐wavelength infrared range.