Siddha Pimputkar

Siddha Pimputkar
Lehigh University · Department of Materials Science and Engineering

B.S. Mechanical Engineering, Ph.D. Materials

About

23
Publications
11,689
Reads
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2,703
Citations
Citations since 2016
11 Research Items
1917 Citations
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
Additional affiliations
August 2016 - present
Lehigh University
Position
  • Professor (Assistant)
August 2016 - present
Lehigh University
Position
  • Professor
October 2012 - August 2016
University of California, Santa Barbara
Position
  • PostDoc Position
Education
August 2006 - August 2012
August 2002 - June 2006
Illinois Institute of Technology
Field of study
  • Mechanical Engineering
August 1995 - June 2002
Kantonsschule Limmattal
Field of study
  • Mathematical and Scientific Gymnasium

Publications

Publications (23)
Article
Full-text available
Titanium zirconium molybdenum (TZM) is a high strength at high temperature alloy with favorable properties for use in high temperature structural applications. Use of TZM in high pressure, gas-containing autoclave systems was recently demonstrated for the ammonothermal method. Use of indium (In) in the system is desired, though there is a general l...
Article
The ammonothermal method has been extensively studied for the last two decades because of its potential to produce high-quality bulk gallium nitride (GaN) boules at low cost. Currently, the ammonothermal literature lacks in situ, internal fluid temperature measurements during the crystal growth process. This study reports on internal fluid temperat...
Article
Native bulk gallium nitride (GaN) has emerged as an alternative for sapphire and silicon as a substrate material for III-N devices. While quasi-bulk GaN substrates are currently commercially available, single crystal GaN substrates are considered essential for future high performance light emitters and power devices. The ammonothermal method is cur...
Article
The ammonothermal method is one of the most promising candidates for large-scale bulk GaN growth due to its scalability and high crystalline quality. However, emphasis needs to be put on understanding the incorporation and effects of impurities during growth. This article discusses how impurities are incorporated in different growth zones in basic...
Article
Due to the disparity between observed gallium nitride (GaN) growth under conditions for which literature reports normal solubility, GaN solubility in supercritical NH3-Na containing solutions was re-evaluated. Isothermal gravimetric experiments on polycrystalline GaN were performed in the temperature range (T =415–650 °C) for which retrograde growt...
Article
We report recent results of bulk GaN crystal growth using the sodium flux method in a new crucible-free growth system. We observed a (0001) Ga face (+c-plane) growth rate >50 µm/hr for growth at a N2 overpressure of ~5 MPa and 860 °C, which is the highest crystal growth rate reported for this technique to date. Omega X-ray rocking curve (ω-XRC) mea...
Article
Single crystal, bulk gallium nitride (GaN) crystals were grown using the basic ammonothermal method in a high purity growth environment created using a non-hermetically sealed molybdenum (Mo) capsule and compared to growths performed in a similarly designed silver (Ag) capsule and capsule-free René 41 autoclave. Secondary ion mass spectrometry (SIM...
Article
This paper discusses promising materials for use as internal, non-load bearing components as well as molybdenum-based alloys for autoclave structural components for an ammonothermal autoclave. An autoclave was constructed from the commercial titanium-zirconium-molybdenum (TZM) alloy and was found to be chemically inert and mechanically stable under...
Article
Though several methods exist to produce bulk crystals of gallium nitride (GaN), none have been commercialized on a large scale. The sodium flux method, which involves precipitation of GaN from a sodium-gallium melt supersaturated with nitrogen, offers potentially lower cost production due to relatively mild process conditions while maintaining high...
Article
Polarization controlled Fourier transform infrared (FTIR) absorption measurements were performed on a high quality m-plane ammonothermal GaN crystal grown using basic chemistry. The polarization dependence of characteristic absorption peaks of hydrogen-related defects at 3000–3500 cm−1 was used to identify and determine the bond orientation of hyd...
Article
Improvements to the growth of nitride crystals in ammonothermal growth environments can be achieved through improved autoclave designs, purity, and use of in situ monitoring techniques. Given the limited data available on the stability of materials in supercritical ammonia solutions, this study intends to broaden the known dataset by experimentally...
Article
Erhebliche Energieeinsparungen sind dank einer einzigen Erfindung möglich: der blauen Leuchtdiode. Die Forschung an GaN-basierte blauen LEDs resultierte nicht nur in einer effizienten weißen Lichtquelle, sondern hat viele weitere Anwendungs- und Forschungsperspektiven eröffnet. Die an der Entwicklung der blauen LED in erster Linie beteiligten Forsc...
Article
Significant gains in energy savings now underway can be traced to a single invention-the blue light emitting diode. GaN-based blue LED technology not only resulted in efficient white light sources, but continues to enable a host of applications and scientific inquiries. The researchers primarily responsible for the development of the blue LED were...
Article
Gallium Nitride (GaN) and its alloys form a promising material system for optoelectronic and electronic devices. Heteroepitaxial growth of GaN on sapphire and SiC, while viable, introduces threading dislocations (between 1E8 – 1E11 cm^-2), mismatches in thermal expansion coefficients, and limitations on available growth orientations other than the...
Patent
Full-text available
Boron-containing compounds, gasses and fluids are used during ammonothermal growth of group-Ill nitride crystals. Boron-containing compounds are used as impurity getters during the ammonothermal growth of group-Ill nitride crystals. In addition, a boron-containing gas and/or supercritical fluid is used for enhanced solubility of group-Ill nitride i...
Article
Light-emitting diodes (LEDs) fabricated from gallium nitride (GaN) have led to the realization of high-efficiency white solid-state lighting. Currently, GaN white LEDs exhibit luminous efficacy greater than 150 lm W−1, and external quantum efficiencies higher than 60%. This has enabled LEDs to compete with traditional lighting technologies, such as...
Article
Full-text available
New scintillators for high-resolution gamma ray spectroscopy have been identified, grown and characterized. Our development efforts have focused on two classes of high-light-yield materials: europium-doped alkaline earth halides and cerium-doped garnets. Of the halide single crystals we have grown by the Bridgman method-SrI<sub>2</sub>, CaI<sub>2</...
Article
Full-text available
Solid-state lighting using light-emitting diodes (LEDs) has the potential to reduce energy consumption for lighting by 50% while revolutionizing the way we illuminate our homes, work places, and public spaces. Nevertheless, substantial technical challenges remain in order for solid-state lighting to significantly displace the well-developed convent...

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