Curriculum Vitae
NILANJAN HALDER
Nevada Nanotechnology Center
Dept. of Electrical & Computer Engineering
University of Nevada, Las Vegas (UNLV)
NEVADA - 89154-4026; USA.
Ph: 1-702-895-3775 (Nano Lab), 1-702-895-4183 (Dept. Office)
Fax: 1-702-895-407
email: nhalder@egr.unlv.edu
Education:
1. Post Doctoral Research [July, 2006 – present]
Department of Electrical and Computer Engg.
University of Nevada, Las Vegas (UNLV)
Field of Research: Nanotechnology
Advisor: Dr. Biswajit Das, Professor, Dept of Electrical Engg., UNLV.
2. Doctoral Research [October, 2001 – June, 2006]
Department of Electronic Science
University of Calcutta (Kolkata, India)
Dissertation: “Studies on the Electrical and Optical Characteristics of Epitaxial
In1-xGaxP and Dilute GaAsN”
Advisor: Dr. S.Dhar, Professor, Dept. of Electronic Sc., University of Calcutta.
3. Master of Science in Applied Physics [August, 2001]
Sikkim Manipal Institute of Technology
Sikkim Manipal University, (Gangtok, India)
4. Bachelor of Science in Physics [July, 1999]
Bhairab Ganguly College
University of Calcutta (Kolkata, India)
Research Interests:
Epitaxy and thin films, Semiconductor devices and heterostructure, Optoelectronics and
Nanoelectronics, High Vacuum systems.
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Research career
Presently appointed as Post-Doctoral Research Scholar, in the Department of Electrical
and Computer Engg., University of Nevada, Las Vegas.
Started working for Ph.D. thesis under the supervision of Prof. S. Dhar from 15.10.01
and registered for Ph.D. program under Dept. of Electronic Science, Calcutta University
on 7.8.2002.
Appointed as a Project Assistant from 8th April 2002 to 31st March 2003 in a AICTE (All
India Council for Technical Education) funded project entitled “Growth of InGaP layer
by liquid phase epitaxy and studies of its device structure” in the Department of
Electronic Science (C.U.).
Appointed as a Project Officer in a Ministry of Information Technology (Govt. of India)
funded project entitled “LPE growth of GaSb and InGaAsSb for mid infrared
Photodetectors” in the same department under Prof. S. Dhar from March 2004 to January
2006.
Helped in the successful running of the project “Development of Ultra high Purity Gallium
for Epitaxial and Optoelectronic Applications” funded by Defence Research and
Development Organization (DRDO), Govt. of India, in the Dept. of Electronic Science,
Calcutta University.
Undertook the charge of the PG lab “Semiconductor materials & Optoelectronics
Laboratory” as an instructor in the same department. Also involved in regular
maintenance of the lab and designing experiments for the PG students.
Peer Advisor: Helped eight (8) graduate students in the successful completion of the
Master’s project under the Electronic Science program of the University of Calcutta
through regular laboratory research work.
Awards & Fellowships
1. National Scholarship in Secondary Exam. (West Bengal Board of Secondary Exam.)
1993, awarded by Ministry of Human Resource Development, Govt. of India.
2. Rai Bahadur Jogendranath Ghosh Overseas Scholarship of the University of Calcutta
for the year 2006-2007 for pursuing Post Doctoral studies.
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Research Expertise:
Doctoral Research
My field of specialization includes “ III-V compound semiconductor growth and
characterization, optoelectronics”. During my postgraduate research I was involved in
extensive Liquid Phase Epitaxial growth of two technologically important semiconductor
materials InGaP and GaAsN. A large part of my research was related to optimization of
the layer properties and heterojunction characteristics through suitable modification of
the growth technique. The electrical and optical properties of the grown layers were
studied through various techniques like temperature dependent Hall Measurements, High
Resolution X-ray Diffraction measurements, optical transmission measurements,
photoconductivity, photocapacitance and photoluminescence measurements. In
characterizing the semiconductor layers emphasis was given on the detection and
physical origin of defects, deeplevels and impurities and measurement of the electrical
effects, which they produce.
Material and device characterization
In the course of my research, I did detailed characterization and measurements on
materials and devices using the following techniques
- Temperature ( 70-300 K) dependent Hall measurements
- Electrical (C-V, I-V) measurements of metal-semiconductor Schottky diodes
fabricated on the epitaxially grown layers
- Low temperature (10 K) photoconductivity and photocapacitance
measurements (experimental set up consists of Kiethley source measure unit,
Lock in amplifier, Optical chopper, Helium Cryogenerator etc.)
Post Doctoral Research
At UNLV I am doing research in nanofabrication techniques such as the
nonlithographic template based fabrication technique which involves the electrochemical
annodisation and subsequent etching. I also have hands on experience with sputtering and
nanocluster deposition using Ultra High Vacuum Oxford Nanocluster deposition system
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Summary of the Doctoral (Ph.D.) research work
The work is devoted to the growth and characterization of two technologically
important III-V compound semiconductors, InGaP and dilute GaAsN, pseudomorphically
grown on <100> semiinsulating or n+ GaAs substrates. The layers for the study were
grown by the in-house horizontal liquid phase epitaxy (LPE) system in the Department of
Electronic Sience, Calcutta University, employing sliding boat technique under an
ambient of ultrapure hydrogen .
The important results derived from the overall study are the following
1. Properties of Fe doped and undoped InGaP layers grown on GaAs substrates by LPE
are investigated. Fe in III-V compounds is known to produce a deep acceptor level, which
is responsible for compensation of donors. Low temperature photocapacitance and
photocurrent experiments on our layers detect a 1.0 eV hole trap, which is present in Fe
doped layers only and is related to Fe concentration in the layers. It is suggested that the
1.0 eV trap is the center responsible for compensation of donors.
2. The possibility of reducing the background impurities in InGaP layer grown by LPE,
by adding small quantities of Er to the growth melt has been explored. Hall
measurements showed that Er reduces the background impurities in the grown InGaP
layers. Slight increase in layer-substrate mismatch, as a result of Er addition due to the
formation of ErP in the growth melt is revealed by double crystal X-ray diffraction
(DCXRD) experiments. Photocapacitance experiments indicated the presence of one 0.66
eV electron trap and one 0.95 eV hole trap in the Er doped material only. A similar 0.9
eV hole trap was also detected in Fe-doped InGaP and is attributed to phosphorous
vacancy.
3. GaAsN layers for the first time have been successfully grown by LPE using a saturated
melt of GaAs in Ga to which little amounts of polycrystalline GaN was added as the
source of nitrogen. Room temperature Fourier transform infrared (FTIR) absorption
indicated the presence of nitrogen in the grown layers. High-resolution X-ray diffraction
studies indicated change in lattice constant of the layers with respect to the substrate from
which nitrogen content in the layer was obtained. Bandgap reduction of about 100 meV
due to nitrogen incorporation in the layers grown from LPE growth melt containing 1
wt% GaN, was measured by optical transmission measurements and low temperature
photoluminescence (PL) measurements, from which again the nitrogen content in the
sample was found out. In addition, we have done photocurrent measurements on reverse
biased gold Schottky barrier diodes fabricated on the same layer surface to further
substantiate the results obtained from the above experiments.
4. The origin and nature of the deep levels present in our LPE GaAsN samples were
investigated. Low temperature photocurrent and photocapacitance measurements
revealed the presence of an electron trap with ionization energy of 0.65 – 0.67 eV in the
as-grown layers whose origin was related to interstitial (N-N)As defects. High temperature
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annealing of the layers almost removed the trap and new electron traps at 0.8 eV and 0.9
eV were produced. It has been suggested that during the annealing process, (N-NAs)
defects, due to their lower energy of formation, are converted to more thermally stable
(AsGa – NAs) or (AsN)As defects which might be the source of the new electron traps. It is
further supported by performing the experiment on GaAsN layers grown with varying
nitrogen content. The addition of Er to the same growth melt and subsequent high
temperature treatment was found to remove nitrogen from the grown layer as revealed by
PL experimenmts and no electron trap was detected in the same materials. This result
confirmed that the electron traps detected in our LPE- grown GaAsN layers are due to
nitrogen. Thus through a novel experiment (Er treatment of melt), a direct proof of
relation of the observed traps in the LPE grown material to nitrogen, was demonstrated.
5. Also some work on LPE growth of GaSb layers and purification of GaSb LPE-melt by
adding small amount of Er to the growth melt have been done. Work on the growth of
GaSbN and InGaAsSbN layers on GaSb substrate was performed. HRXRD and EDAX
measurements on the grown GaSbN layer showed that a considerable percentage of
nitrogen is incorporated in the layers. This again is the first successful report of the
growth of GaSbN using LPE technique.
List of Publications
Archival Journal Articles
1. Observation of 0.7eV electron trap in dilute GaAsN layers grown by Liquid Phase
Epitaxy
S.Dhar, N.Halder, J.Kumar, B.M. Arora
Applied Physics Letters (American Institute of Physics) – August 9, 2004 – Volume 85,
Issue 6, pp. 964-966
2. Detailed studies on the origin of nitrogen-related electron traps in dilute GaAsN layers
grown by liquid phase epitaxy
S.Dhar, N.Halder, A.Mondal, Bhavtosh Bansal and B.M.Arora
Semiconductor Science and Technology (Institute of Physics, U. K.)
December 2005 -Volume20, Issue 12, pp. 1168-1172.
3. Investigation of Deep Level Traps in Dilute GaAsN Layers Grown by Liquid Phase
Epitaxy
S.Dhar, N.Halder, A.Mondal
Thin Solid Films, Elsevier Journal (in press) [ doi:10.1016 / j.tsf.2006.07.116 ]
4. Growth of dilute GaSbN layers by liquid-phase epitaxy
A.Mondal, T.D.Das, N.Halder, S.Dhar, J.Kumar
Journal of Crystal Growth, Vol- 297, pp. 4-6 (2006).
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Conference / Symposium presentations
1. Characteristics of Metalorganic Vapor Phase Epitaxial In0.49Ga0.51P grown on Liquid
Phase Epitaxial In0.49Ga0.51P/ GaAs.
S.Dhar, Sarani Basu, N.Halder, B.M.Arora.
Sixth International Conference on Optoelectronics, Fiber Optics and Photonics
(PHOTONICS-2002), TIFR, Mumbai, India (2002)
2. Deep levels in InGaP layers doped with Fe.
S.Dhar and N.Halder.
XII International Workshop on the Physics of Semiconductor Devices (IWPSD-03),
Madras IIT, Chennai (2003).
3. Photoemission spectroscopy of Si-implanted GaN
S.Dhar, Sarani Basu, N.Halder
XII International Workshop on the Physics of Semiconductor Devices (IWPSD-03),
Madras IIT, Chennai (2003).
4. Transport properties of n-type GaAs from the analysis of temperature dependent
capacitance voltage technique
Ashok Rao, Kaustav Chakrabourty, Rema Bhattacharya, Nilanjan Halder.
Indian Science Congress (2003).
5. Rare-earth and Transition metal doped InGaP: Growth and Characterization.
S.Dhar and N.Halder.
International conference on Communication, Device and Intelligent Systems, Jadavpur
University, Calcutta (2004).
6. Growth of Dilute Nitrides by Liquid Phase Epitaxy.
S.Dhar, N.Halder, J.Kumar.
International conference on Communication, Device and Intelligent Systems, Jadavpur
University, Calcutta (2004).
7. Dilute GaAsN layers grown by liquid phase epitaxy.
N.Halder and S.Dhar.
International conference on Computers and Devices for Communication, University of
Calcutta, Kolkata (2004).
8. Liquid Phase Epitaxial Growth and Characterization of Dilute III-V Nitrides.
S.Dhar, N.Halder, J.Kumar, B.M.Arora.
International conference on Optoelectronics Technology, Jalgaon, North Maharashtra
University (2004).
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9. Dilute GaAsN layers grown by Liquid Phase Epitaxy
N.Halder
XVII Young Physicists’ Colloquium of The Indian Physical Society (YPC – 2004), Saha
Inst. of Nuclear Physics, Kolkata (2004).
10. Nitrogen – related Deep Levels in Dilute III-V Nitrides Grown by Liquid Phase
Epitaxy
S.Dhar, N.Halder, A.Mondal
Seventh International Conference on Optoelectronics, Fiber Optics and Photonics
(PHOTONICS-2004), Kochin University, Kochi. (Dec 2004)
11. Er Gettering of Impurities in GaSb Layers Grown by Liquid Phase Epitaxy
S.Dhar, A.Mondal, N.Halder
Seventh International Conference on Optoelectronics, Fiber Optics and Photonics
(PHOTONICS-2004), Kochin University, Kochi. (Dec 2004)
12. Investigation of Deep Level Traps in Dilute GaAsN Layers Grown by Liquid Phase
Epitaxy
S.Dhar, N.Halder, A.Mondal
3rd International Conference on Materials for Advanced Technologies (ICMAT-2005),
Singapore (3-8 July, 2005).
13. Structural, optical and transport properties of ZnO Thin Films
R.Chandramohan, L.S.Hsu, V.N.Mani, S.Dhar, N.Halder
3rd International Conference on Materials for Advanced Technologies (ICMAT-2005),
Singapore (3-8 July, 2005).
14. Nitrogen-related deep levels in dilute GaAsN layers grown by liquid phase epitaxy
N.Halder
Young Scientists’ Colloquium 2005, Material Research Society of India (MRSI, Kolkata
Chapter), Saha Institute of Nuclear Physics, Kolkata (July 08, 2005).
15. Growth and characterization of dilute GaSbN and InGaAsSbN layers
A. Modal, N. Halder, and S. Dhar
International Conference on Electronic and Photonic Materials, Devices and Systems
(EPMDS-2006), University of Calcutta, Kolkata (January 4-6, 2006)
16. Characteristics of dilute GaAsN layers grown by liquid phase epitaxy
N. Halder, A. Mondal, and S. Dhar
International Conference on Electronic and Photonic Materials, Devices and Systems
(EPMDS-2006), University of Calcutta, Kolkata (January 4-6, 2006)
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17. Liquid Phase Epitaxial growth of Fe-doped and Er-gettered InGaP layers
N.Halder
Presented in One day seminar on “Material Physics” organized by Material Research
Society of India (Kolkata Chapter) and The West Bengal Academy of Science and
Technology to commemorate The World Year of Physics, Saha Institute Auditorium,
SINP, Kolkata. (19 th September, 2005)
Workshop / School attended
1. Indo-Japan Workshop on Crystal Growth and Applications of Advanced Materials for
Optoelectronics
Crystal Growth Center, Anna University, Chennai-600 025, India (Dec 7-10, 2004).
2. International Workshop on Crystal Growth and Characterization of Advanced
Materials
Crystal Growth Center, Anna University, Chennai-600 025, India (Jan 9-13, 2006).
3. nanoAware: An Nanotechnology Awareness Program ( Under Technical Education
Quality Improvement [TEQIP] Program)
University College of Science and Technology, University of Calcutta, Kolkata-700009
(March 24-25, 2006)
4. Theme Meeting on Self-assembly Routes for Nanotech Materials (SARNaM-06)
Bhaba Atomic Research Center (BARC), Mumbai (April 26/28, 2006)
Professional training
4th ASME Nano-Training Boot Camp; University of Minnesota, Minneapolis, US (10-14
July, 2006)
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