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Kumar M.,Indian Institute of Science | Kumar M.,Bharat Heavy Electricals Ltd. | Roul B.,Indian Institute of Science | Roul B.,Bharat Heavy Electricals Ltd. | And 5 more authors.
Journal of Nanoparticle Research | Year: 2011

One of the scientific challenges of growing InN quantum dots (QDs), using Molecular beam epitaxy (MBE), is to understand the fundamental processes that control the morphology and distribution of QDs. A systematic manipulation of the morphology, optical emission, and structural properties of InN/Si (111) QDs is demonstrated by changing the growth kinetics parameters such as flux rate and growth time. Due to the large lattice mismatch, between InN and Si (∼8%), the dots formed from the Strannski-Krastanow (S-K) growth mode are dislocated. Despite the variations in strain (residual) and the shape, both the dot size and pair separation distribution show the scaling behavior. We observed that the distribution of dot sizes, for samples grown under varying conditions, follow the scaling function. © 2010 Springer Science+Business Media B.V. Source


Bhat T.N.,Indian Institute of Science | Roul B.,Indian Institute of Science | Roul B.,Bharat Heavy Electricals Ltd. | Rajpalke M.K.,Indian Institute of Science | And 4 more authors.
Applied Physics Letters | Year: 2010

The present work explores the temperature dependent transport behavior of n-InN nanodot/p-Si (100) heterojunction diodes. InN nanodot (ND) structures were grown on a 20 nm InN buffer layer on p -Si(100) substrates. These dots were found to be single crystalline and grown along [001] direction. The junction between these two materials exhibits a strong rectifying behavior at low temperatures. The average barrier height (BH) was determined to be 0.7 eV from current-voltage-temperature, capacitance-voltage, and flat band considerations. The band offsets derived from built-in potential were found to be Δ E C =1.8 eV and Δ EV =1.3 eV and are in close agreement with Anderson's model. © 2010 American Institute of Physics. Source


Rajpalke M.K.,Indian Institute of Science | Roul B.,Indian Institute of Science | Roul B.,Bharat Heavy Electricals Ltd. | Kumar M.,Indian Institute of Science | And 4 more authors.
Scripta Materialia | Year: 2011

We report the structural and optical properties of a-plane GaN film grown on r-plane sapphire substrate by plasma-assisted molecular beam epitaxy. High resolution X-ray diffraction was used to determine the out-of-plane and in-plane epitaxial relation of a-plane GaN to r-plane sapphire. Low-temperature photoluminescence emission was found to be dominated by basal stacking faults along with near-band emission. Raman spectroscopy shows that the a-GaN film is of reasonably good quality and compressively strained. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source


Kumar M.,Indian Institute of Science | Kumar M.,Bharat Heavy Electricals Ltd. | Rajpalke M.K.,Indian Institute of Science | Bhat T.N.,Indian Institute of Science | And 5 more authors.
Materials Letters | Year: 2011

Indium nitride (InN) epilayers have been successfully grown by nitrogen-plasma-assisted molecular beam epitaxy (NPA-MBE) on Si (111) substrates using different buffer layers. Growth of a (0001)-oriented single crystalline wurtzite-InN layer was confirmed by high resolution X-ray diffraction (HRXRD). The Raman studies show the high crystalline quality and the wurtzite lattice structure of InN films on the Si substrate using different buffer layers and the InN/β-Si3N4 double buffer layer achieves minimum FWHM of E2 (high) mode. The energy gap of InN films was determined by optical absorption measurement and found to be in the range of ~ 0.73-0.78 eV with a direct band nature. It is found that a double-buffer technique (InN/β-Si3N4) insures improved crystallinity, smooth surface and good optical properties. © 2011 Elsevier B.V. All rights reserved. Source


Bhat T.N.,Indian Institute of Science | Rajpalke M.K.,Indian Institute of Science | Roul B.,Indian Institute of Science | Roul B.,Bharat Heavy Electricals Ltd. | And 4 more authors.
Physica Status Solidi (B) Basic Research | Year: 2011

Investigations were carried out on the ambient condition oxidation of self-assembled, fairly uniform indium nitride (InN) quantum dots (QDs) fabricated on p-Si substrates. Incorporation of oxygen in to the outer shell of the QDs was confirmed by the results of transmission electron microscopy (TEM), X-ray photoemission spectroscopy (XPS). As a consequence, a weak emission at high energy (∼1.03eV) along with a free excitonic emission (0.8eV) was observed in the photoluminescence spectrum. The present results confirm the incorporation of oxygen into the lattice of the outer shell of InN QDs, affecting their emission properties. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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