Shi et al. Nanoscale Res Lett 2011, 6:50 http://www.nanoscalereslett.com/content/6/1/50 N A N O E X P R E S S Open Access Determination of InN/Diamond Heterojunction Band Offset by X-ray Photoelectron Spectroscopy K Shi1*, DB Li2*, HP Song1, Y Guo1, J Wang1, XQ Xu1, JM Liu1, AL Yang1, HY Wei1, B Zhang1, SY Yang1, XL Liu1*, QS Zhu1, ZG Wang1 Abstract Diamond is not only a free standing highly transparent window but also a promising carrier confinement layer for InN based devices, yet little is known of the band offsets in InN/diamond system. X-ray photoelectron spectroscopy was used to measure the energy discontinuity in the valence band offset (VBO) of InN/diamond heterostructure. The value of VBO was determined to be 0.39 ± 0.08 eV and a type-I heterojunction with a conduction band offset (CBO) of 4.42 ± 0.08 eV was obtained. The accurate determination of VBO and CBO is important for the application of III-N alloys based electronic devices. Introduction Among the group III nitrides, InN is of great interest because of its extremely high predicted electron mobility [1], small effective mass [2,3], and large electron satura- tion drift velocity [4]. With the latest progress in improving the film quality these years, InN film has been considered to be able to meet the requirements for application to practical devices [5,6]. It is expected to be a highly promising material for the fabrication of high performance,high electron mobility transistor (HEMT) due to its electronic properties. Moreover, the re-evalua- tion of the InN bandgap and subsequent findings [7,8] have opened up interesting opportunities for using InN in new applications, such as high-efficiency solar cells [9], solid state lighting [10-12], and 1.55 μm emission for fiber optics [13,14]. As the hardest material with high optical transparency from ultraviolet to infrared range, diamond is an excellent transparent window for InN based photoelectric devices mentioned above. It can also be used as lens coatings for infrared transmissions. The bandgap of diamond at room temperature is ~5.45 eV, so it is a promising carrier confinement layer for InN based HEMT, which requires a larger bandgap * Correspondence: shikai@semi.ac.cn; lidb@ciomp.ac.cn; xlliu@semi.ac.cn 1Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, 100083, Beijing, People’s Republic of China. 2Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 Dong Nan Hu Road, 130033, Changchun, People’s Republic of China. Full list of author information is available at the end of the article barrier to confine electrons. Furthermore, because of the combination of its unique electronic and thermal prop- erties, diamond plays a vital or somewhat irreplaceable role in some special applications, such as in abominable environments and military fields. Up to now, the GaN/ diamond system has already been studied by a lot of groups [15,16]. However, there is lack of experimental data available on the interface band alignment para- meters for InN/diamond system. X-ray photoelectron spectroscopy (XPS) has been demonstrated to be a direct and powerful tool for measuring the valence band offsets (VBOs) of heterojunctions [6,17-19]. In this let- ter, we report an experimental measurement of the VBO in InN/diamond heterojunction by XPS. Experimental Three samples were used in our XPS experiments, namely, a 350-nm-thick InN layer grown on c-plane sapphire, a 2-mm-thick single-crystal diamond synthe- sized at high temperature and high pressure(HTHP), and a ~5-nm-thick InN grown on diamond. InN films in this study were grown by horizontal low-pressure metal-organic chemical vapor deposition, as reported elsewhere [19].The crystal structures were characterized using the high-resolution X-ray diffraction (HRXRD) apparatus at Beijing Synchrotron Radiation Facility (BSRF). The incident X-ray beam is monochromized to 0.154791 nm by a Si (111) monocrystal. According to the XRD results, single-crystal diamond (400) and wurt- zite InN (002) were obtained. Both diamond and InN in © 2010 Shi et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.