Energy-band alignments at ZnO/Ga2O3 and Ta2O5/Ga2O3 heterointerfaces by X-ray photoelectron spectroscopy and electron affinity rule

Zeng Liu,Zeng Liu,Weihua Tang,Weihua Tang,Xia Wang,Xia Wang,Yuanyuan Liu,Yuanyuan Liu,Yusong Zhi,Yusong Zhi,Peigang Li,Peigang Li,Xiaolong Wang,Xiaolong Wang,Wanjun Li

doi:10.1063/1.5112067

Abstract

Wide bandgap oxide semiconductors have been a hot topic in electronic and optoelectronic technologies. The oxide heterojunctions provide many significant favorable properties in devices. The energy-band alignments at the heterointerfaces between oxides play a key role in the functional electronics. In this work, we studied the band alignments of ZnO/Ga2O3 and Ta2O5/Ga2O3 heterojunctions. The valence band offsets of Ta2O5/Ga2O3 and ZnO/Ga2O3 heterojunctions were determined by X-ray photoelectron spectroscopy. The Ta2O5/Ga2O3 heterojunction exhibits a type II band alignment with a valence band offset of −0.24±0.02eV and a conduction band offset of 1.06±0.02eV, while the ZnO/Ga2O3 heterojunction has a type I band alignment accompanied with a valence band offset of 0.14±0.05eV and a conduction band offset of 1.47±0.05eV, which has no obvious difference with results by the electron affinity rule. The investigation for Ta2O5/Ga2O3 and ZnO/Ga2O3 heterojunctions could provide a useful guidance of design and physical analysis of their further applications in corresponding heterogeneous structured devices.

Highlights

The valence band offsets of Ta2O5/Ga2O3 and ZnO/Ga2O3 heterojunctions were determined by X-ray photoelectron spectroscopy
The Ta2O5/Ga2O3 heterojunction exhibits a type II band alignment with a valence band offset of À0:24 + 0:02 eV and a conduction band offset of 1:06 + 0:02 eV, while the ZnO/Ga2O3 heterojunction has a type I band alignment accompanied with a valence band offset of 0:14 + 0:05 eV and a conduction band offset of 1:47 + 0:05 eV, which has no obvious difference with results by the electron affinity rule
The investigation for Ta2O5/Ga2O3 and ZnO/Ga2O3 heterojunctions could provide a useful guidance of design and physical analysis of their further applications in corresponding heterogeneous structured devices

Summary

Introduction

The study of heterojunctions for their employment in electronics could be traced back to the 1960s.1,2 After a few decades, from the view of current developments, the heterojunction has verified its advantages over the homojunction for device fabrications and performances in many fields, which is mainly on account of their different bandgaps and inconsecutive energy bands at semiconductor-semiconductor heterointerfaces.[3,4] Owing to the optical transparency, high mobility, and easy fabrication on flexible substrates, oxide semiconductors have been utilized as the mainstream in various devices such as photovoltaic cells, flat panel displays, smart windows, sensors, transparent electrodes, photodetectors, and power devices.[5,6,7,8,9] Benefiting from many excellent characteristics at heterogeneous interfaces, oxide interfaces give a birthplace of new discoveries and functional sciences and have been widely employed in modern electronic devices.[8,9,10,11,12] Band alignment between one oxide and another plays a decisive role in governing the functions of oxides heterostructured electronics.[3,9,10,11,12]To provide meaningful guidance for designing and constructing heterostructured oxide-based devices, the band offsets at conduction and valence band edges are very important.[9]. We studied the band alignments of ZnO/Ga2O3 and Ta2O5/Ga2O3 heterojunctions. The valence band offsets of Ta2O5/Ga2O3 and ZnO/Ga2O3 heterojunctions were determined by X-ray photoelectron spectroscopy.

Results

Conclusion