Fabrication and characterization of heteroepitaxial p-n junction diode composed of wide-gap oxide semiconductors p-ZnRh2O4/n-ZnO

A reactive solid-phase epitaxy technique was applied to fabricate all-oxide transparent p-n heterojunctions composed of p-ZnRh2O4 and n-ZnO thin layers. Polycrystalline ZnRh2O4 was deposited on a ZnO epitaxial layer at room temperature. Thermal annealing of the bilayer sample at 950 °C in air converts the polycrystalline ZnRh2O4 layer to an epitaxial single-crystalline layer. The resultant p-n heterojunctions have an abrupt interface and exhibit a distinct rectifying I–V characteristic. The threshold voltage is ∼2 V, agreeing well with the band-gap energy of ZnRh2O4. It also exhibits photovoltage with UV-light illumination, which originates mainly from the n-ZnO layer.