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

Ren-Hao Chang,Tai-Hong Chen,Tsung-Hsin Lee,Kai-Chao Yang,Shiau-Lu Yao,Day-Shan Liu,Li-Wen Lai

doi:10.1155/2013/560542

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.

Highlights

To accomplish a high-performance zinc oxide- (ZnO-) based optoelectronic device, the formation of a quality contact between ZnO and electrode is essential
With the aim to achieve a quality ZnO-based Schottky diode, a homogeneity indium tin oxide- (ITO-) ZnO cosputtered film was deposited onto the undoped ZnO layer as an ohmic contact electrode, followed by the surface modification processes combined with the preetching process, using the diluted hydrochloric acid (HCl) solution, and the surface treatment, using the dilute H2O2 and (NH4)2Sx solutions, respectively, on the undoped ZnO layer prior to the Ni/Au Schottky metal deposition
The increase in the Schottky barrier height between the ZnO and Ni/Au contact was found to be deeply correlated to the decrease in the carrier concentration of the ZnO layer surface modified by the combination process of the etching and the surface treatments, as derived from the C-V measurements

Summary

Introduction

To accomplish a high-performance zinc oxide- (ZnO-) based optoelectronic device, the formation of a quality contact between ZnO and electrode is essential. Various ZnO surface passivation processes, such as chemical preparation with specific acid or organic solution, plasma bombardment, and activated light irradiation, were processed to achieve a quality ZnO-based Schottky diode [7,8,9,10]. With the aim to achieve a quality ZnO-based Schottky diode, a homogeneity indium tin oxide- (ITO-) ZnO cosputtered film was deposited onto the undoped ZnO layer as an ohmic contact electrode, followed by the surface modification processes combined with the preetching process, using the diluted HCl solution, and the surface treatment, using the dilute H2O2 and (NH4)2Sx solutions, respectively, on the undoped ZnO layer prior to the Ni/Au Schottky metal deposition. The mechanisms responsible for the improvement of the ZnO-based Schottky diode were comprehensively investigated by using the X-ray photoelectron spectroscopy (XPS) and room-temperature photoluminescence (RTPL) measurements

Experiment

Results and Discussions

Conclusions