Magnesium-composition engineering of <i>p</i> -type Ni1−xMgxO thin films for enhanced self-powered <b> <i>β</i> </b> -Ga2O3 photodetection

Abstract

Mg-composition-tuned p-type Ni1−xMgxO thin films were developed by radio frequency co-sputtering for solar-blind β-Ga2O3 heterojunction photodetectors. Mg incorporation significantly modifies the structural and optical properties of the films, inducing a transition in the preferential crystal orientation, reducing the crystallite size, and widening the optical bandgap from 3.71 to 4.23 eV. The electrical transport properties are also strongly affected, with tunable carrier concentration and mobility. The resulting heterojunction devices exhibit self-powered operation with enhanced photoresponse. The responsivity increases from 2.34 to 13.20 mA/W, and the specific detectivity reaches 4.0 × 1012 Jones with increasing Mg content. The improved performance is attributed to the optimized structural, electrical, and band-alignment properties, together with the enhanced built-in potential at equilibrium, which promotes more efficient photogenerated carrier separation and transport. These results demonstrate the potential of Ni1−xMgxO as a tunable p-type material for solar-blind photodetection.