Photo Sensitivity Enhanced by the Modulation of Oxide Thickness in MIS(p) Structure

Abstract

Photodetector for MIS(p) structure with surrounding concentric gate resulted in significant interest. We propose the modulation of oxide thickness to improve the sensitivity of the photodetector. By measuring various oxide thickness from 2.2 to 3.4 nm, we find that the dark current under deep depletion region of MIS structure strongly depends on oxide thickness. As the oxide thickness increases, the dark current in center MIS decreases and thus effectively increases the sensitivity. We suggest that the reduced dark current resulted from less modulation of Schottky barrier height while surrounding gate current of the thick device is lower. By properly biasing the gate electrode, the ratio of light to dark current of MIS structure is 9 for 2.5nm but is 148 for 3nm. The sensitivity of the thick oxide device is enhanced to 16 times with respect to the thin one.