The interface between oxide/oxide layers shows an inhomogeneous charge transport behavior, which reveals a high conductivity owing to interface-doped. One typical example is the hetero-interface between ZnO film and other wide band gap oxides (e.g., Al₂O₃, TiO₂, and HfO₂). It is thus quite evident that the ZnO/other oxides hetero-interface contains high density electron carriers effectively screening the gate-induced electric field. Thus, an extremely weak gate modulation in ZnO film was showed, resulting in very low on/off ratio of 1.69 in top-gate field-effect-transistor (TG-FET) configuration. So, to extend the usage of ZnO TG-FET is not quite possible toward further practical application. Herein, we clarified the correlation of inhomogeneous region in oxide/oxide hetero-junction by systematically study. Our work suggests that a self-assembly of molecules (SAM) buffer layer is suitable for tuning the inhomogeneous charge transport in ZnO film, which not only reduces the interface trap density, but also effectively enhances the gate electric field modulation at the hetero-interface. We further report the robust fabrication of TG-FET arrays based on ZnO thin film, using an ultra-thin alkylphosphonic acid molecule monolayer as buffer layer. Our device demonstrates a pronounced ultrahigh on/off ratio of ≥ 10⁸, which is 8-order of magnitude higher than that of a device without buffer layer. For the highly reliable arrays, our device exhibits a high yield of over 93% with an average on/off ratio of ~10⁷ across the entire wafer scale, mobility (18.5 cm²/(V·s)), an extended bias-stressing (~ 2,000 s) and long-stability (~ 150 days) under ambient conditions.

Graphene (Gr)/Si-based optoelectronic devices have attracted a lot of academic attention due to the simpler fabrication processes, low costs, and higher performance of their two-dimensional (2D)/three-dimensional (3D) hybrid interfaces in Schottky junction that promotes electron-hole separation. However, due to the built-in potential of Gr/Si as a photodetector, the I_ph/I_dark ratio is often hindered near zero-bias at relatively low illumination intensity. This is a major drawback in self-powered photodetectors. In this study, we have demonstrated a self-powered van der Waals heterostructure photodetector in the visible range using a Gr/hexagonal boron nitride (h-BN)/Si structure and clarified that the thin h-BN insertion can engineer asymmetric carrier transport and avoid interlayer coupling at the interface. The dark current was able to be suppressed by inserting an h-BN insulator layer, while maintaining the photocurrent with minimal decrease at near zero-bias. As a result, the normalized photocurrent-to-dark ratio (NPDR) is improved more than 10⁴ times. Also, both I_ph/I_dark ratio and detectivity, increase by more than 10⁴ times at -0.03 V drain voltage. The proposed Gr/h-BN/Si heterostructure is able to contribute to the introduction of next-generation photodetectors and photovoltaic devices based on graphene or silicon.