Office of Principal Scientific Advisor

Bhubaneshwar, India

Office of Principal Scientific Advisor

Bhubaneshwar, India
SEARCH FILTERS
Time filter
Source Type

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.


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 7 more authors.
Materials Research Bulletin | Year: 2010

High-quality GaN epilayers were grown on Si (1 1 1) substrates by molecular beam epitaxy using a new growth process sequence which involved a substrate nitridation at low temperatures, annealing at high temperatures, followed by nitridation at high temperatures, deposition of a low-temperature buffer layer, and a high-temperature overgrowth. The material quality of the GaN films was also investigated as a function of nitridation time and temperature. Crystallinity and surface roughness of GaN was found to improve when the Si substrate was treated under the new growth process sequence. Micro-Raman and photoluminescence (PL) measurement results indicate that the GaN film grown by the new process sequence has less tensile stress and optically good. The surface and interface structures of an ultra thin silicon nitride film grown on the Si surface are investigated by core-level photoelectron spectroscopy and it clearly indicates that the quality of silicon nitride notably affects the properties of GaN growth. © 2010 Elsevier Ltd. All rights reserved.


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.


Roul B.,Indian Institute of Science | Roul B.,Bharat Heavy Electricals Ltd. | Rajpalke M.K.,Indian Institute of Science | Bhat T.N.,Indian Institute of Science | And 5 more authors.
Journal of Applied Physics | Year: 2011

InN/GaN heterostructure based Schottky diodes were fabricated by plasma-assisted molecular beam epitaxy. The temperature dependent electrical transport properties were carried out for InN/GaN heterostructure. The barrier height and the ideality factor of the Schottky diodes were found to be temperature dependent. The temperature dependence of the barrier height indicates that the Schottky barrier height is inhomogeneous in nature at the heterostructure interface. The higher value of the ideality factor and its temperature dependence suggest that the current transport is primarily dominated by thermionic field emission (TFE) other than thermionic emission (TE). The room temperature barrier height obtained by using TE and TFE models were 1.08 and 1.43 eV, respectively. © 2011 American Institute of Physics.


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

InN layers were directly grown on Ge substrate by plasma-assisted molecular beam epitaxy (PAMBE). The valence band offset (VBO) of wurtzite InN/Ge heterojunction is determined by X-ray photoemission spectroscopy (XPS). The valence band of Ge is found to be 0.18 ± 0.04 eV above that of InN and a type-II heterojunction with a conduction band offset (CBO) of ∼ 0.16 eV is found. The accurate determination of the VBO and CBO is important for the design of InN/Ge based electronic devices. © 2011 Elsevier B.V. All rights reserved.


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.


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.


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.


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

Negative differential capacitance (NDC) has been observed in n-GaN/p-Si heterojunctions grown by plasma assisted molecular beam epitaxy (PAMBE). The NDC is observed at low frequencies 1 and 10 kilohertz (kHz) and disappeared at a higher testing frequency of 100 kHz. The NDC is also studied with temperature and found that it has disappeared above 323 °C. CurrentVoltage (IV) characteristics of n-GaN /p-Si heterojunction were measured at different temperatures and are attributed to the space-charge-limited current (SCLC). A simple model involving two quantum states is proposed to explain the observed NDC behavior. © 2010 Elsevier Ltd. All rights reserved.


Rajpalke M.K.,Indian Institute of Science | Bhat T.N.,Indian Institute of Science | Roul B.,Indian Institute of Science | Roul B.,Bharat Heavy Electricals Ltd. | And 6 more authors.
Journal of Crystal Growth | Year: 2011

Non-polar a-plane GaN films were grown on an r-plane sapphire substrate by plasma assisted molecular beam epitaxy (PAMBE). The effect of growth temperature on structural, morphological and optical properties has been studied. The growth of non-polar a-plane (1 1 -2 0) orientation of the GaN epilayers were confirmed by high resolution X-ray diffraction (HRXRD) study. The X-ray rocking curve (XRC) full width at half maximum of the (1 1 -2 0) reflection shows in-plane anisotropic behavior and found to decrease with increase in growth temperature. The atomic force micrograph (AFM) shows island-like growth for the film grown at a lower temperature. Surface roughness has been decreased with increase in growth temperature. Room temperature photoluminescence shows near band edge emission at 3.4343.442 eV. The film grown at 800 °C shows emission at 2.2 eV, which is attributed to yellow luminescence along with near band edge emission. © 2010 Elsevier B.V. All rights reserved.

Loading Office of Principal Scientific Advisor collaborators
Loading Office of Principal Scientific Advisor collaborators