Defect engineering of RF sputtered Mg doped ZnO thin film for efficient photodetector application

Abstract

Mg0.1Zn0.9O thin films were deposited using RF magnetron sputtering system on p-Si substrate, which were then annealed at various temperatures in air. The experiments showed that the crystallinity and surface roughness of the Mg0.1Zn0.9O films increased with the annealing temperature, meanwhile red shift was observed in the optical bandgap. The field emission scanning electron microscope (FESEM) analysis revealed that the surface morphology becomes more homogeneous with annealing temperature. A near band emission (NBE) and three deep level emission (DLE) (violet, blue and weak green emission) were observed from PL analysis for all the samples (as-deposited, 100 °C, 300 °C, 500 °C, and 700 °C). A red shift in the NBE (from 352 nm to 371 nm) and also disappearance of DLE at around 540 nm was observed with increase in annealing temperature. The MgZnO/p-Si device (500 °C) exhibits great photosensitivity (24-fold enhancement) as compare to as-deposited device because the thin film (TF) has high surface to volume ratio and the massive amount of photogenerated carriers. In addition, MgZnO/p-Si (500 °C) demonstrated quick device response with a rise time of 0.78 s and a fall time of 0.26 s under white light illumination.