The International Journal of Engineering And Science (IJES) ||Volume|| 1 ||Issue|| 1 ||Pages|| 09-12 ||2012|| ISSN: 2319 – 1813 ISBN: 2319 – 1805
Enhancement of different electrolytes on Porous In0.27Ga0.73N using photo-electrochemical etching A. Y. Hudeish1, A. Mahgoob 2 1, 2
Physics Department, Hodeidah University, Hodeidah, Yemen.
--------------------------------------------------- Abstract -------------------------------------------------This article reports the properties and the behavior of In 0.27 Ga0.73 N during the photoelectrochemical etching process using four different electrol ytes. The measurements show that the porosity strongly depends on the electrolyte and highl y affects the surface morphology of etched samples, which has been revealed by scanni ng electron microscopy (S EM) i mages. Peak intensity of the photoluminescence (PL) spectra of the porous In0.27 Ga0.73 N samples was observed to be enhanced and strongly depend on the electrolytes. Among the samples, there is a little di fference in the peak position indicati ng that the change of porosity has little influence on the PL peak shift, while it highly affecting the peak intensity. Raman spectra of porous In0.27 Ga0.73 N under four different solution exhi bit phonon mode E2 (high), A1 (LO), A1 (TO) and E2 (low). There was a red shift in E2 (high) in all samples, indicating a relaxati on of stress in the porous In0.27 Ga0.73 N surface with respect to the underlyi ng single crystalline epitaxial In 0.27 Ga0.73 N . Raman and PL intensities were high for samples etched in H2SO4:H2O2 and KOH followed by the samples etched in HF:HNO3 and in HF:C2 H5 OH. Keywords— Electrolyte; InGaN; Photo-electrochemical etching; Porosity.
----------------------------------------------------------------------------------------------------------------Date of Submission: 20, October 2012, Date of Publication: 10, November 2012, ----------------------------------------------------------------------------------------------------------------I.
INTRODUCTION
The In GaN ternary alloy system receives a great deal of attention among III-nit ride co mpound semiconductors because of its direct band gap tuning fro m 0.7 eV for InN to 3.4 eV for GaN, giv ing In GaN great potential for the design of high efficiency optoelectronic devices that operate in the IR, v isible, and UV reg ions of the electro magnetic spectrum [1]. Porous III-n itride co mpounds are considered as pro mising materials for optoelectronics [2] and chemical and biochemical sensors [3] because of their unique optical and electronic properties compared with bulk materials [4,5]. The formation of a porous nanostructure has been widely reported for crystalline silicon [6]. In addition to porous silicon research, attention has also been focused on other porous semiconductors, such as GaAs [7] and GaN [8-10]. Interest in porous semiconductor materials arises fro m the fact that these materials can act as sinks for threading dislocation and are able to acco mmodate strain. Po rous semiconductor materials are also useful for understanding the fundamental properties of nanoscale structures for the development of nanotechnology. Research on porous GaN is strongly driven by the robustness of porous GaN, including its excellent thermal, mechanical, and chemical stabilities that make it h ighly desirable for
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optical applicat ions [11]. Many researchers [4,12-14] have used the photoelectrochemical etching (PEC) technique to synthesize porous GaN. The PEC technique is more suitable and cheaper compared with other techniques for producing high density nanostructures with controlled pore size and shape [4]. Electrolyte, current density and illu mination are the main factors that affect electrochemical etching. Hydrofluoric acid (HF) is the most common ly used material in etching GaAs and GaN [15]. In the current study, the PEC technique is used to synthesize porous InGaN nanostructures at various current densities. To the best of our knowledge, this study is the first to report of porous In GaN by using four different electrolytes as the PEC technique.
II.
EXPERIMENTAL
In 0.27 Ga0.73 N/GaN/AlN epitaxial layers were grown on Si(111) substrate by using a plasma assisted mo lecular beam ep itaxy (PA-M BE) system (Veeco Gen II). High-purity sources, such as galliu m (7N), alu minu m (6N5), and indiu m (7N), were installed in the Knudsen cells. Reactive nitrogen species were generated by channeling high-purity nitrogen to a radio frequency (RF) source. The resultant nitrogen plasma was at a nitrogen pressure of
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