Raman scattering and Rutherford backscattering studies on InN films grown by plasma-assisted molecular beam epitaxy Yee Ling Chung a , Xingyu Peng b , Ying Chieh Liao a , Shude Yao b , Li Chyong Chen c , Kuei Hsien Chen d , Zhe Chuan Feng a, ⁎ a Institute of Photonics & Optoelectronics, and Department of Electrical Engineering, National Taiwan University, Taipei 106, Taiwan b State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China c Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan d Institution of Atomic and Molecular Sciences, Academia Sinica, Taipei 115, Taiwan abstract article info Available online 4 May 2011 Keywords: InN Plasma-assisted molecular beam epitaxy Rutherford backscattering Raman scattering Photoluminescence A series of InN thin films was grown on sapphire substrates via plasma-assisted molecular beam epitaxy (PA-MBE) with different nitrogen plasma power. Various characterization techniques, including Hall, photoluminescence, Raman scattering and Rutherford backscattering, have been employed to study these InN films. Good crystalline wurtzite structures have been identified for all PA-MBE grown InN films on sapphire substrate, which have narrower XRD wurtzite (0002) peaks, showed c-axis Raman scattering allowed longitudinal optical (LO) modes of A 1 and E 1 plus E 2 symmetry, and very weak backscattering forbidden transverse optical (TO) modes. The lower plasma power can lead to the lower carrier concentration, to have the InN film close to intrinsic material with the PL emission below 0.70 eV. With increasing the plasma power, high carrier concentration beyond 1 × 10 20 cm -3 can be obtained, keeping good crystalline perfection. Rutherford backscattering confirmed most of InN films keeping stoichiometrical In/N ratios and only with higher plasma power of 400 W leaded to obvious surface effect and interdiffusion between the substrate and InN film. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The development in blue/UV light emitting diodes (LED) and laser diodes (LD), and also high-frequency transistors operating at high powers and temperatures [1,2] has proved the benefits of the nitride materials system. Among III-nitride compound semiconductors, which are successfully employed in high-brightness blue and green light-emitting devices, InN has caused more concerns in recent years [3,4]. Indium nitride (InN) is an important III-nitride semiconductor with many potential applications. The use of InN and its alloys with GaN and AlN makes it possible to extend the emission of nitride-based LEDs from ultraviolet to near infrared region. InN was predicted to have lowest effective mass for electrons in all the III-nitride semiconductors [5,6], which leads to high mobility and high saturation velocity. The electron transport in wurtzite InN was studied using an ensemble Monte Carlo method [7–10]. It was found that InN exhibits an extremely high peak drift velocity at room temperature. This suggests that there may be distinct advantages offered by using InN in high frequency centimeter and millimeter wave devices. The transient electron transport, which is expected to be the dominant transport mechanism in submicron-scale devices, was also studied in InN [11,12]. The use of InN-based optoelectronic devices offers the potential of an environmental-friendly red emitter with no toxic element, which may replace GaAs-based devices. In addition, InN is a potential material for low cost solar cells with high efficiency. Yamamoto et al. proposed InN for a top cell material of a two-junction tandem solar cell [13]. The InN/Si system recently showed InN as a good plasma filter material for the widely used GaSb and GaInAsSb photovoltaic cells in thermo-photovoltaic system, which show good performance [14]. In this paper, we have reported that InN films with different carrier concentrations were successfully grown by plasma-assisted molecular beam epitaxy (PA-MBE) using a low temperature AlN buffer layer. These samples were analyzed by Hall measurement, photolumines- cence (PL), Raman scattering and Rutherford backscattering studies. The relation between the plasma power and the quality of InN films is discussed. 2. Experimental details 2.1. Sample growth InN films were grown by plasma-assisted MBE, using a SVTA model SVT-V-2 [3], with various N 2 -plasma power levels in the range of 200 to 400 W on sapphire substrates after nitridation process. The radio-frequency (RF) plasma source is the key component of a MBE Thin Solid Films 519 (2011) 6778–6782 ⁎ Corresponding author. Tel.: + 886 2 3366 3543; fax: + 886 2 2367 7467. E-mail addresses: sdyao@pku.edu.cn (S. Yao), fengzc@cc.ee.ntu.edu.tw (Z.C. Feng). 0040-6090/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2011.04.203 Contents lists available at ScienceDirect Thin Solid Films journal homepage: www.elsevier.com/locate/tsf