Self-powered n-Mg_xZn_1-xO/p-Si photodetector improved by alloying-enhanced piezopotential through piezo-phototronic effect

A high-performance self-powered ZnO-based photodetector is developed by enhancing piezopotential through alloying with Mg. An n-Mg_xZn_1-xO thin film (x=0.05 and 0.2) with a strong c axis preferred orientation in the wurtzite phase is grown on a p-type Si substrate by magnetron co-sputtering. The piezotronics and piezo-phototronics properties are studied by determining the dependence of electrical and optical characteristics of preferentially orientated Mg_xZn_1-xO thin films on strain. The performance of the self-powered photodetectors increases with Mg content due to the increase of the piezoelectric coefficient by the alloying process, and thus an enhanced piezopotential. In addition, the photosensing results show that the piezo-phototronic effect can boost the output current density and voltage of the self-powered photodetector by more than 100%. The sensitivity of the photodetector with Mg_0.20Zn_0.80O is over 6-fold greater than that of the photodetector with Mg_0.05Zn_0.95O. The results demonstrate a strong dependence on Mg content in Mg_xZn_1-xO for the piezo-phototronic effect. The developed material is thus a promising candidate for ultra-high-sensitivity photodetectors.