Ultra‐Sensitive Cubic‐ITO/Silicon Photodiode via Interface Engineering of Native SiOx and Lattice‐Strain‐Assisted Atomic Oxidation

Abstract

AbstractA highly orientated cubic indium tin oxide (c‐ITO)/native SiOx/n‐Si Schottky photodiode with negligible electronic noise is demonstrated. This extraordinary property is achieved via simple interface engineering, which combines native SiOx, facile air‐annealing, and the resulting ITO‐lattice‐strain‐assisted oxidation of proximal underlying Si atoms. An exceptionally well‐passivated ITO/n‐Si interface is realized, which leads to a heretofore unreported single‐atom‐thin inversion layer observed via transmission electron microscopy imaging. The device exhibits a record‐low dark current density of ≈3 × 10–8 A cm–2 at −5 V, a tenfold reduction over the lowest reported value. Additional excellent optoelectronic properties achieved include self‐powered operation, high quantum efficiency, fast time response, and ultra‐high sensitivity for low illumination signals. Interface characterization reveals that ITO‐lattice relaxation and oxygen diffusion during annealing create a highly ordered c‐ITO crystal and an extended ≈2.2 nm SiOx interlayer formed via atomic oxidation of the underlying pristine Si, thus rendering a high‐quality interface. Moreover, the Schottky barrier is further enhanced by the presence of negatively charged sub‐stoichiometric silicon oxide interlayer. These results bring forth new insights in the surface atomic oxidation process and the significance of natively grown SiOx which together contribute to the realization of economic highly sensitive photodetectors.