Ravi Pathak

Indian Institute of Technology Delhi

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Rajendra Singh

Indian Institute of Technology Delhi

U. Dadwal

Indian Institute of Technology Delhi

A. K. Kapoor

Indian Institute of Technology Delhi

M.O. Garg

Indian Institute of Science Bangalore

Vinay Gupta

University of Delhi

Bhera Ram Tak

Indian Institute of Technology Delhi

Che‐Hao Liao

King Abdullah University of Science and Technology

Samuthira Nagarajan

Central University of Tamil Nadu

A. Claverie

Centre d’Élaboration de Matériaux et d’Études Structurales

Ankur Kulshreshta

NIMS University

Cooperative Institutions

Indian Institute of Technology Delhi

King Abdullah University of Science and Technology

Indian Institute of Technology Bombay

University of Delhi

CSIR National Physical Laboratory of India

Centre d’Élaboration de Matériaux et d’Études Structurales

Centre National de la Recherche Scientifique

Université de Toulouse

Solid State Physics Laboratory

Ministry of Defence

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Study of hydrogen implantation-induced blistering in GaSb for potential layer transfer applications

Journal of Physics D Applied Physics (2017)

Ravi Pathak U. Dadwal Rajendra Singh

10.1088/1361-6463/aa7522

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Citations (10)

Effect of surface passivation process for AlGaN/GaN HEMT heterostructures using phenol functionalized-porphyrin based organic molecules

Journal of Applied Physics (2018)

M.O. Garg Tejas R. Naik Ravi Pathak Valipe Ramgopal Rao Che‐Hao Liao

In this work, we investigate an unexplored possibility of passivating the charged surface states on AlGaN/GaN high electron mobility transistor (HEMT) heterostructures by using organic molecules. This has further led to remarkable enhancement in the electrical properties of rectifying metal-semiconductor contacts on AlGaN/GaN. Phenol functionalized Zinc metallated-Tetra Phenyl Porphyrin (Zn-TPPOH) organic molecules were adsorbed on AlGaN/GaN via the solution phase to form a molecular layer (MoL). The presence of the MoL was confirmed using X-ray Photoelectron Spectroscopy (XPS). The thickness of the MoL was assessed as ∼1 nm, using Spectroscopic Ellipsometry and cross-sectional Transmission Electron Microscopy. XPS peak-shift analyses together with Kelvin Probe Force Microscopy revealed that the molecular surface modification reduced the surface potential of AlGaN by approximately 250 meV. Consequently, the Barrier height (ideality factor) of Ni Schottky diodes on AlGaN/GaN was increased (reduced) significantly from 0.91 ± 0.05 eV (2.5 ± 0.31) for Ni/AlGaN/GaN to 1.37 ± 0.03 eV (1.4 ± 0.29) for Ni/Zn-TPPOH/AlGaN/GaN. In addition, a noteworthy decrement in the reverse current from 2.6 ± 1.93 μA to 0.31 ± 0.19 nA at −5 V (∼10 000 times) was observed from Current-Voltage (I-V) measurements. This surface-modification process can be fruitful for improving the performance of AlGaN/GaN HEMTs, mitigating the adverse effects of surface states and polarization in these materials.

Passivation

10.1063/1.5049873

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Observation of Large Surface Area Exfoliation in Hydrogen Implanted Ge

physica status solidi (a) (2020)

Ravi Pathak U. Dadwal A. K. Kapoor Rajendra Singh

Large surface area exfoliation of the hydrogen (H)‐implanted Ge is investigated in this work. H + ions with a fluence of 1 × 10 17 cm −2 are implanted in Ge samples at liquid nitrogen and room temperature (RT). The formation of surface blisters and craters is observed in the samples annealed between 300 and 450 °C after implantation. Interestingly, samples implanted at RT show large surface area exfoliation extending over several hundreds of micrometer region after annealing. Secondary ion mass spectroscopy (SIMS) and depth‐resolved Raman spectroscopy are used to characterize the depth profile of implanted H + ions and stress in the damage region, respectively. The formation of the damage band filled with extended planar defects in the form of nanocracks is observed using a cross‐sectional transmission electron microscope (TEM). The physical understanding of the H‐induced internal pressure and stress in the surface blisters/craters is carried out using Föppl–von Karman theory of thin plates.

Blisters

Exfoliation joint

10.1002/pssa.202000182

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Citations (1)

Understanding of MoS2/GaN Heterojunction Diode and its Photodetection Properties

Scientific Reports (2018)

Monika Moun Mukesh Kumar M.O. Garg Ravi Pathak Rajendra Singh

Fabrication of heterojunction between 2D molybdenum disulfide (MoS2) and gallium nitride (GaN) and its photodetection properties have been reported in the present work. Surface potential mapping at the MoS2/GaN heterojunction is done using Kelvin Probe Force Microscopy to measure the conduction band offset. Current-voltage measurements show a diode like behavior of the heterojunction. The origin of diode like behavior is attributed to unique type II band alignment of the heterojunction. The photocurrent, photoresponsivity and detectivity of the heterojunction are found to be dependent on power density of the light. Photoresponse investigations reveal that the heterojunction is highly sensitive to 405 nm laser with very high responsivity up to 105 A/W. The heterojunction also shows very high detectivity of the order of 1014 Jones. Moreover, the device shows photoresponse in UV region also. These observations suggest that MoS2/GaN heterojunction can have great potential for photodetection applications.

Photodetection

Photocurrent

Band offset

Band diagram

10.1038/s41598-018-30237-8

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Citations (110)

Point defects induced work function modulation of β-Ga2O3

Applied Surface Science (2018)

Bhera Ram Tak Sheetal Dewan Anshu Goyal Ravi Pathak Vinay Gupta

Pulsed Laser Deposition

10.1016/j.apsusc.2018.09.236

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Citations (94)

Large area stress free Si layer transfer onto Corning glass substrate using ion-cut

Semiconductor Science and Technology (2018)

Ravi Pathak U. Dadwal Kamal Soni Rajendra Singh

We report on the large area stress free single crystal silicon (Si) layer transfer onto glass substrate using hydrogen ion (H+) implantation and heterogeneous direct wafer bonding (DWB) (ion-cut process). Si wafers were implanted with H+ ions at room temperature followed by the DWB between the Si wafer and glass substrate. Post-implantation annealing studies were performed at different temperatures. The root mean square surface roughness of the H-implanted Si wafer and glass substrate was measured to be 0.3 nm and 0.5 nm, respectively. At an annealing temperature of 330 °C, a thin layer of the Si wafer was transferred onto the glass substrate. The average thickness of the transferred layer was found to be ~605 nm with surface roughness of 4 nm. Raman spectroscopy confirmed that the transferred Si layer was stress free and retained its crystallinity. Large area transfer of high quality stress free Si-on-glass substrate is demonstrated using heterogeneous DWB and ion-cut process.

10.1088/1361-6641/aaf611

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Experimental Investigation of Vibration Based Surface Roughness Prediction System

Ravi Pathak Ankur Kulshreshta

‘Mass Customization’ is an attempt to provide unique values to the customers in an efficient manner. In the present work, that unique value chosen is required surface quality instead of ‘Best’ quality which has become a choice of today’s customized market. Prediction of surface roughness is an essential requirement for any computer numeric controlled (CNC) machinery. Poor control on the desired surface roughness generates rebellious parts and results in increase in cost and loss of productivity due to rework. Surface roughness value is a result of several process variables among which vibration is of great significant. In this study, full factorial design of experiment (DOE) approach is applied to find the optimum cutting parameters to obtain predicted surface roughness in turning at computer numeric controlled (CNC) cell. Dry turning is performed for aluminum alloy bars using diamond shaped carbide tool insert. The analysis of variance (ANOVA) and correlation technique are applied to study the performance characteristics of machining parameters with surface roughness and cutting tool vibrations. Feed rate and bi-axial cutting tool vibrations are observed to be main parameters affecting surface roughness. Regression equation is formulated for estimating predicted values of surface roughness. Finally, to illustrate the effectiveness of the regression equation, the rate of error is found between the actual and predicted surface roughness values.

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Study of surface exfoliation induced by hydrogen implantation and annealing in GaSb (100) substrates

Materials Science in Semiconductor Processing (2021)

Ravi Pathak U. Dadwal A. K. Kapoor Maxime Vallet A. Claverie

Exfoliation joint

10.1016/j.mssp.2021.105998

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Citations (1)