Investigation of structural and optical properties of GaN on flat and porous silicon Saleh H. Abud a, * , Abbas M. Selman b , Z. Hassan c a Department of Physics, Faculty of Science, University of Kufa, Najaf, Iraq b Department of Pharmacognosy and Medicinal Plants, Faculty of Pharmacy, University of Kufa, Najaf, Iraq c Institute of Nano Optoelectronic Research and Technology (INOR), Universiti Sains Malaysia,11800 Penang, Malaysia article info Article history: Received 21 April 2016 Received in revised form 17 July 2016 Accepted 19 July 2016 Available online 21 July 2016 Keywords: III-V materials Porous Si High resolution X-ray diffraction abstract In this work, gallium nitride (GaN) layers were successfully grown on Flat-Si and porous silicon (PSi) using a radio frequency-magnetron sputtering system. Field emission scan- ning electron microscopy and atomic force microscopy images showed that the grown film on Flat-Si had smoother surface, even though there were some cracks on it. Furthermore, the X-ray diffraction measurements showed that the peak intensity of all the grown layers on PSi was higher than that of the grown layer on Flat-Si. Our detailed observation showed that PSi is a promising substrate to obtain GaN films. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction III-nitride structured compounds such as GaN have been widely investigated and applied in various optoelectronics and electronic devices [1]. Devices based on GaN are usually grown on foreign substrates such as SiC because of the absence of a bulk of large-area native substrate [2]. At the same time, there is an interest in Si due to it being low cost, has reasonable thermal conductivity and large area availability compared with SiC and sapphire. Therefore, GaN on Si is a promising candidate offering broad areas of applications, including light emitting diodes (LEDs) [3], pH sensors [4] and dye-sensitized solar cells [5]. However, it is difficult to grow high-quality GaN films on Si, therefore, buffer layer such as AlN has been used to reduce the defect density in GaN film. PSi is considered to be a flexible layer to avoid the use a buffer layer; therefore, it is a promising substrate to relief the strain caused by lattice mismatch involved in the GaN on Flat-Si as well as in the GaAs on a Flat-Si system [6e8]. Many research works have been devoted to grow GaN on Flat-Si [9e12] and a few groups tried to grow GaN on PSi with a buffer layer. Therefore, we had attempted in this work to grow GaN layers on PSi without any compliant layer. 2. Experimental procedure Photoelectrochemical etching (PECE) technique was used to synthesize the porous structures of 275mm-thick n-type Si (100) wafers. The etching solution was a mixture of (49%) aqueous HF and (99.99%) C 2 H 5 OH with different volume ratios of 1:3, 1:4 and 1:5 under UV illumination and a constant current density (25 mA/cm 2 ) for 15 min. The etching cell was made of * Corresponding author. E-mail address: salehhasson71@gmail.com (S.H. Abud). Contents lists available at ScienceDirect Superlattices and Microstructures journal homepage: www.elsevier.com/locate/superlattices http://dx.doi.org/10.1016/j.spmi.2016.07.017 0749-6036/© 2016 Elsevier Ltd. All rights reserved. Superlattices and Microstructures 97 (2016) 586e590