Surface Modification on the Sputtering-Deposited ZnO Layer for ZnO-Based Schottky Diode

Abstract

We prepare a zinc oxide- (ZnO-) based Schottky diode constructed from the transparent cosputtered indium tin oxide- (ITO-) ZnO ohmic contact electrode and Ni/Au Schottky metal. After optimizing the ohmic contact property and removing the ion-bombardment damages using dilute HCl etching solution, the dilute hydrogen peroxide (H2O2) and ammonium sulfide (NH4)2Sxsolutions, respectively, are employed to modify the undoped ZnO layer surface. Both of the Schottky barrier heights with the ZnO layer surface treated by these two solutions, evaluated from the current-voltage (I-V) and capacitance-voltage (C-V) measurements, are remarkably enhanced as compared to the untreated ZnO-based Schottky diode. Through the X-ray photoelectron spectroscopy (XPS) and room-temperature photoluminescence (RTPL) investigations, the compensation effect as evidence of the increases in the O–H and OZnacceptor defects appearing on the ZnO layer surface after treating by the dilute H2O2solution is responsible for the improvement of the ZnO-based Schottky diode. By contrast, the enhancement on the Schottky barrier height for the ZnO layer surface treated by using dilute (NH4)2Sxsolution is attributed to both the passivation and compensation effects originating from the formation of the Zn–S chemical bond andVZnacceptors.