On the Photo-Carriers Dynamic Regulation by Piezo-Phototronic Effect in Metal-Oxide–Semiconductor Tunneling Junction

The piezo-phototronic effect can modulate the dynamics of photo-generated carriers by utilizing external-strain–induced piezoelectric charges (piezo-charges). Most of the current researches focus on the modulation effect on the optoelectronic properties of p–n junctions. There are only a few studies focusing on the metal-oxide–semiconductor (MOS) structures. In this work, a PEDOT:PSS/Al₂O₃/n-ZnO tri-layer MOS tunneling junction is fabricated and the piezo-phototronic effect on its photo-carriers dynamic and performances is systematically investigated. The photoresponsivity to 365 nm laser illumination is reduced because of the negative piezo-charges generated at the Al₂O₃/n-ZnO interface. Meanwhile but unexpectedly, the similar phenomenon utilizing the positive piezo-charges at the Al₂O₃/n-ZnO interface is observed. The in-depth working mechanisms are carefully investigated by analyzing the effect of piezo-charges on the energy band diagram. Strain induced piezo-charges could feasibly adjust the intermediate oxide layer's barrier height and width so that the tunneling effect can be efficiently modulated by the piezo-phototronic effect, leading to the effective control over the MOS tunneling junction's photo-carriers dynamic and corresponding photoresponses. This work provides an in-depth understanding for the piezo-phototronic effect on the MOS tunneling junction and provides guidance for the subsequent researches on the coupling of piezo-phototronic effect and tunneling effect.