Valence band offset of InN/BaTiO 3 heterojunction measured by X-ray photoelectron spectroscopy
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NANO EXPRESS
Open Access
Valence band offset of InN/BaTiO3 heterojunction measured by X-ray photoelectron spectroscopy Caihong Jia1,2, Yonghai Chen1*, Yan Guo1, Xianglin Liu1, Shaoyan Yang1, Weifeng Zhang2 and Zhanguo Wang1
Abstract X-ray photoelectron spectroscopy has been used to measure the valence band offset of the InN/BaTiO3 heterojunction. It is found that a type-I band alignment forms at the interface. The valence band offset (VBO) and conduction band offset (CBO) are determined to be 2.25 ± 0.09 and 0.15 ± 0.09 eV, respectively. The experimental VBO data is well consistent with the value that comes from transitivity rule. The accurate determination of VBO and CBO is important for use of semiconductor/ferrroelectric heterojunction multifunctional devices. Introduction The semiconductor-ferroelectric heterostructures have attracted much attention due to their large potential for new multifunctional electronic and optoelectronic device applications [1-5]. Hysteresis properties of the ferroelectric polarization allow for bistable interface polarization configuration The polarization coupling between the fixed permanent semiconductor dipole and the switchable ferroelectric dipole can be exploited to modify the electronic and the optical properties of a semiconductor heterostructure. Recently, GaN-based high electron mobility transistor devices have been integrated on ferroelectric LiNbO3, providing the compact optoelectronic/electronic chips with increased cost savings and added functionality [6]. The semiconductor-ZnO/ferroelectric-BaTiO3 (BTO) heterostructure metal-insulatorsemiconductor field-effect transistors have been demonstrated, in which the polarization of the BTO can be used to control the free carrier concentration in the ZnO channel [7]. In order to fully exploit the advantages of semiconductor-ferroelectric heterostructures, other combinations such as InN/BTO should be explored. As a remarkable ferroelectric material with a high relative permittivity, BTO can be used as a gate dielectric for InN-based field-effect transistor. More importantly, InN/BTO heterojunction is promising for fabricating optical and electrical devices since oxidation treatment * Correspondence: [email protected] 1 Key Laboratory of Semiconductor Material Science, Institute of Semiconductors, Chinese Academy of Science, P.O. Box 912, Beijing 100083, PR China Full list of author information is available at the end of the article
is found to reduce the surface electron accumulation of InN films [8]. For heterostructure devices, it is important to accurately determine the valence and the conduction band offsets, which dictate the degree of charge carrier separation and localization. However, up to date, there is lack of experiment data available on the interface band alignment parameters for InN/BTO heterojunction. In this letter, we determine the VBO as well as conduction band offset (CBO) values of the InN/BTO heterojunction using X-ray photoelectron spectroscopy (XPS).
Experimental Three samples (bulk BTO, thick InN/BTO
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