Showing papers by "Mahesh Kumar published in 2013"
TL;DR: The temperature dependent electrical transport behavior of n-n InGaN/Si heterostructures grown by plasma-assisted MBE was studied in this paper, where structural characteristics of the epilayers were evaluated high-resolution X-ray diffraction and composition of InGaNs was estimated from photoluminescence spectra using standard Vegard's law.
11 citations
TL;DR: In this paper, the substrate effect on InN nanostructures grown by droplet epitaxy has been studied and the morphologies of InN nano-structures were investigated by field emission scanning electron microscopy (FESEM).
Abstract: The substrate effect on InN nanostructures grown by droplet epitaxy has been studied. InN nanostructures were fabricated on Si(111), silicon nitride/Si(111), AlN/Si(111) and Ge(100) substrates by droplet epitaxy using an RF plasma nitrogen source. The morphologies of InN nanostructures were investigated by field emission scanning electron microscopy (FESEM). The chemical bonding configurations of InN nanostructures were examined by x-ray photoelectron spectroscopy (XPS). Photoluminescence spectrum slightly blue shifted compared to the bulk InN, indicating a strong Burstein–Moss effect due to the presence of high electron concentration in the InN dots (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
5 citations
TL;DR: The thermal oxidation process of the indium nitride (InN) nanorods (NRs) was studied and the cracked and burst mechanism for the formation of indium oxide (In2O3) nanostructures by oxidizing the InN NRs at higher temperatures is revealed.
Abstract: The thermal oxidation process of the indium nitride (InN) nanorods (NRs) was studied. The SEM studies reveal that the cracked and burst mechanism for the formation of indium oxide (In2O3) nanostructures by oxidizing the InN NRs at higher temperatures. XRD results confirm the bcc crystal structure of the as prepared In2O3 nanostructures. Strong and broad photoluminescence spectrum located at the green to red region with maximum intensity at 566 nm along with a weak ultraviolet emission at 338 nm were observed due to oxygen vacancy levels and free excitonic transitions, respectively. The valence band onset energy of 2.1 eV was observed from the XPS valence band spectrum, clearly justifies the alignment of Fermi level to the donor level created due to the presence of oxygen vacancies which were observed in the PL spectrum. The elemental ratio In:O in as prepared In2O3 was found to be 42:58 which is in close agreement with the stoichiometric value of 40:60. A downward shift was observed in the Raman peak positions due to a possible phonon confinement effect in the nanoparticles formed in bursting mechanism. Such single junction devices exhibit promising photovoltaic performance with fill factor and conversion efficiency of 21% and 0.2%, respectively, under concentrated AM1.5 illumination.
4 citations
01 Jan 2013
TL;DR: The structural and optical properties of semipolar GaN grown on m-plane sapphire substrates by molecular beam epitaxy were investigated in this article, where an in-plane orientation relationship was found to be 1 -1 0 0] GaN parallel to 1 2-1 0] spphire and -1 -1 2 3] GaNs parallel to 0 0 -0 0 1] sapphires.
Abstract: The structural and optical properties of semipolar (1 1 -2 2) GaN grown on m-plane (1 0 -1 0) sapphire substrates by molecular beam epitaxy were investigated. An in-plane orientation relationship was found to be 1 -1 0 0] GaN parallel to 1 2-1 0] sapphire and -1 -1 2 3] GaN parallel to 0 0 0 1] sapphire for semipolar GaN on m-plane sapphire substrates. The near band emission (NBE) was found at 3.432 eV, which is slightly blue shifted compared to the bulk GaN. The Raman E-2 (high) peak position observed at 569.1 cm(-1), which indicates that film is compressively strained. Schottky barrier height (phi(b)) and the ideality factor (eta) for the Au/semipolar GaN Schottky diode found to be 0.55 eV and 2.11, respectively obtained from the TE model.
2 citations
TL;DR: The structural and optical properties of semipolar GaN grown on m-plane sapphire substrates by molecular beam epitaxy were investigated in this article, where an inplane orientation relationship was found to be [1 -1 0 0] GaN || [1 2-1 0] sapthire and [-1 - 1 2 3] GaNs || [0 0 0 0 1] sappires.
Abstract: The structural and optical properties of semipolar (1 1 -2 2) GaN grown on m-plane (1 0 -1 0) sapphire substrates by molecular beam epitaxy were investigated. An inplane orientation relationship was found to be [1 -1 0 0] GaN || [1 2-1 0] sapphire and [-1 -1 2 3] GaN || [0 0 0 1] sapphire for semipolar GaN on m-plane sapphire substrates. The near band emission (NBE) was found at 3.432 eV, which is slightly blue shifted compared to the bulk GaN. The Raman E2 (high) peak position observed at 569.1 cm–1, which indicates that film is compressively strained. Schottky barrier height (φb) and the ideality factor (η) for the Au/ semipolar GaN Schottky diode found to be 0.55 eV and 2.11, respectively obtained from the TE model. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
2 citations
TL;DR: In this paper, the structural and optical properties of the GaN films grown on p-Si (100) substrates along with photovoltaic characteristics of GaN/p-Si heterojunctions fabricated with substrate nitridation and in absence of substrate Nitridation were investigated.
Abstract: This report focuses on the structural and optical properties of the GaN films grown on p-Si (100) substrates along with photovoltaic characteristics of GaN/p-Si heterojunctions fabricated with substrate nitridation and in absence of substrate nitridation. The high resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), Raman and photoluminescence (PL) spectroscopic studies reveal that the significant enhancement in the structural as well as in the optical properties of GaN epifilms grown with silicon nitride buffer layer when compared with the sample grown without silicon nitride buffer layer. The low temperature PL shows a free excitonic (FX) emission peak at 3.51 eV at the temperature of 5 K with a very narrow line width of 35 meV. Temperature dependent PL spectra follow the Varshni equation well and peak energy blue shifts by similar to 63 meV from 300 to 5 K. Raman data confirms the strain free nature and reasonably good crystallinity of the films. The GaN/p-Si heterojunctions fabricated without substrate nitridation show a superior photovoltaic performance compared to the devices fabricated in presence of substrate nitridation. The discussions have been carried out on the junction properties. Such single junction devices exhibit a promising fill factor and conversion efficiency of 23.36 and 0.12 %, respectively, under concentrated AM1.5 illumination.
1 citations