Areas of Research
Our research falls within the scope of applied physics and materials science/engineering, with particular interests in addressing fundamental challenges arising from the development of advanced semiconductor technologies, on-chip quantum computers, and materials for energy harvesting and harsh-condition sensing.
Description of Research
Our research activities can be grouped into the following topics.
Si-based lasers and other active optical devices in silicon photonics
Building various photonic devices in silicon chips to enable light emission, propagation and detection for optical communications, is a promising approach to keeping pace with increasing demands in speed and volume of data communications by extending silicon electronics into the new age of silicon photonics. As the workhorse in the electronics industry, silicon has attributes of a high refractive index (nSi~3.47 at 1550 nm) and a not-too-small bandgap (Eg~1.1 eV), which allow for cost-effective, high-quality passive optical devices like low-loss waveguides in the telecommunication window, when combining with matured silicon foundry technologies. However, silicon’s indirect bandgap and centrosymmetric lattice structures do not render itself a viable platform for active optical devices such as lasers and high-speed modulators. An electrically driven monolithic Si-based laser has been regarded as the Holy Grain in the semiconductor industry, and despite significant breakthroughs in several research directions, including Ge/Si quantum wells/dots, III-V lasers on Si, Si nanoclusters, and rare-earth doped Si materials, a viable Si-based laser for the semiconductor industry remains unforeseeable. Our research on this path has been focusing on developing strategies of energy transfer to and from erbium emitters for improvements on light emission efficiencies from erbium-doped Si-based materials and erbium compounds on Si. New mechanisms for efficient carrier excitation toward lasing in nanostructured Si are being researched. Our interests also include the development of other active optical devices such as all-Si optical modulators and near-infrared photodetectors, where novel nanostructures in Si would hold the key to overcoming the fundamental constrains.
Doping asymmetry in ultrawide bandgap semiconductors
Due to their higher bandgaps and projected lower production costs, relative to SiC (Eg~3.2 eV) and GaN (Eg~3.4 eV), ultrawide bandgap (UWBG) semiconductors like Ga2O3 (Eg ~4.8 eV) offer great potentials in advancing a broad spectrum of technological capabilities for electric vehicles/ships, 5G/6G communications, high-power electronics, deep-UV optoelectronics and harsh-condition sensing, etc. Currently, the difficulty in achieving both electron and hole conduction in UWBG semiconductors presents the major hindrance to their adoption in the semiconductor industry. UWBG semiconductors are known to have the so-called doping asymmetry problem: they can be readily doped n-type or p-type, but not both in the same material. In the case of Ga2O3, intrinsic and intentionally doped materials are normally of n-type, and attempts to p-type conductivity often end up with deep-level acceptors and hole-trapping polaronic states. The creation of a p-i-n homojunction in an UWBG semiconductor is essential to devices that can fully capitalize on its ultrawide bandgap. For this purpose, we are developing novel ion implantation strategies to address the doping asymmetry problem in UWBG semiconductors through controlling impurity-defect interactions and tailoring semiconductor band structures.
Quantum computing in Si chips
Quantum computing has been conceptually demonstrated in two technological platforms, i.e., superconducting qubits and ion traps. These quantum computers are bulky and delicate, operating at extremely low temperatures, and their further scaling-up for quantum supremacy and beyond is experiencing an exponentially increased level of complexity. The advent of practically accessible quantum computers, even taking years to come, is not meant to displace classical computers out of their positions – The two, each with unique strengths, are for different application domains and they could be combined in a way as electronics and photonics are being integrated in a same Si chip, to expand our information processing capabilities to an unprecedented level. It is important to research routes to quantum computing in solid matrices, particularly in Si chips that can offer a platform to construct scalable quantum computers through existing well-developed semiconductor technologies. To this end, we will leverage our experience in silicon photonics to construct and integrate linear and nonlinear photonic devices in Si chips for programmable quantum information processing. In parallel, we are interested in a hybrid spintronics-photonics approach to creating, manipulating and reading qubits in nanostructured Si chips.
Materials under harsh conditions
In many practical processes encountered in combustion engines, power plants, nuclear reactors and space exploration, etc., materials are subject to extreme conditions of elevated temperatures, high pressure, hostile chemical environments and intense radiations. Understanding mechanisms for materials failure or damage under such extreme conditions is essential for devising reliable, long-lasting components, e.g., fuel delivery system in a nuclear reactor, for these applications. One example is our work in the project led by Lawrence Livermore National Laboratory to understand how structural imperfections (e.g., nanostructures) inhered from materials deposition and processing can impact the ability of dielectric-coated optical mirrors to resist high-power laser beams that are used in the National Ignition Facility for research on laser-induced inertial confinement nuclear fusion. On the other hand, harsh conditions also hamper our ability to monitor in real time the physical parameters such as temperature associated with power generation/combustion processes, e.g., in a jet engine or a nuclear reactor, for meeting strict energy-efficiency and carbon-emission standards. Single-crystal sapphire fibers capable of withstanding high temperatures (melting point > 2000 °C) have long been believed as a promising platform for fiber optic sensing in harsh environments, but unfortunately, unlike silica optical fibers, they do not allow for optical signals to propagate in the single mode demanded for fiber optic sensing due to the lack of fiber cladding (for light confinement). We have developed an innovative technology to enable the formation of buried cladding with excellent high-temperature stability within sapphire fibers (patent US8852695B2, “Optical barriers, waveguides, and methods for fabricating barriers and waveguides for use in harsh environments”). In collaboration with industrial collaborators, we are striving to make sapphire fiber based optic sensing technology a reality for harsh-environment sensing.
- P. B. Mirkarimi, Colin Harthcock, S. Roger Qiu, R. A. Negres, Gabe Guss, Thomas Voisin, J. A. Hammons, C. A. Colla, H. E. Mason, Anton Than, D. Vipin, Mengbing Huang, “Improving the laser performance of ion beam sputtered dielectric thin films through the suppression of nanoscale defects by employing a xenon sputtering gas”, Optical Materials Express 12, 3365 (2022).
- V. N. Peters, S. R. Qiu, C. Harthcock, R. A. Negres, G. Guss, T. Voisin, E. Feigenbaum, C. J. Stolz, D. Vipin and M. Huang, “Investigation of UV, ns-laser damage resistance of hafnia films produced by electron beam evaporation and ion beam sputtering deposition methods”, Journal of Applied Physics 130, 043103 (2021).
- Armando Hernandez, Md Minhazul Islam, Pooneh Saddatkia, Charles Codding, Prabin Dulal, Sahil Agarwal, Adam Janover, Steven Novak, Mengbing Huang, Tuoc Dang, Mike Snure, FA Selim, “MOCVD growth and characterization of conductive homoepitaxial Si-doped Ga2O3”, Results in Physics 25, 104167 (2021).
- Gourav Bhowmik, Yongiang An, Sandra Schujman, Alain Diebold and Mengbing Huang, “Optical second harmonic generation from silicon (100) crystals with process tailored surface and embedded silver nanostructures for silicon nonlinear nanophotonics”, Journal of Applied Physics 128, 165106 (2020).
- Md Minhazul Islam, Naresh Adhikari, Armando Hernandez, Adam Janover, Steven Novak, Sahil Agarwal, Charles L. Codding, Michael Snure, Mengbing Huang and Farida A. Selim, “Direct measurement of the density and energy level of compensating acceptors and their impact on the conductivity of n-type Ga2O3 films”, Journal of Applied Physics 127, 145701 (2020).
- Natasha Tabassum, Vasileios Nikas, Alex E. Kaloyeros, Vidya Kaushik, Edward Crawford, Mengbing Huang and Spyros Gallis, “Engineered telecom emission and controlled positioning of Er3+ enabled by SiC nanophotonic structures”, Nanophotonics 9, 0535 (2020).
- Colin Harthcock, S. Roger Qiu, Paul B. Mirkarimi, Raluca A. Negres, Gabe Guss, Marlon G. Menor, Gourav Bhowmik, and Mengbing Huang, “Origin and effect of film sub-stoichiometry on ultraviolet, ns-laser damage resistance of hafnia single layers”, Optical Materials Express 10, 937 (2020).
- C. Harthcock, S. R. Qiu, R. A. Negres, J. A. Hammons, T. Voisin, G. Guss, A. A. Martin, C. J. Stolz, M. G. Menor, G. Bhowmik and M. Huang, “The impact of nano-bubbles on the laser performance of hafnia films deposited by oxygen assisted ion beam sputtering method”, Applied Physics Letters 115, 251902 (2019).
- Devika Vipin, Nikhil Modi, Tyler Reynolds, Bin Zhang, Natasha Tabassum, Gourav Bhowmik, Vasileios Nikas, Subha Chakraborty, Spyros Gallis, and Mengbing Huang, “Effects of forming gas annealing on luminescence properties of erbium silicate thin films”, AIP Advances 9, 065018 (2019).
- Subha Chakraborty and Mengbing Huang, “Ionoluminescence properties of polystyrene-hosted fluorophore films induced by helium ions of energy 50-350 keV”, Physical Review Materials 1, 055201 (2017).
- Subha Chakraborty, Katherine Harris and Mengbing Huang, “Photoluminescence properties of polystyrene-hosted fluorophore thin films”, AIP Advances 6, 125113 (2016).
- Faisal Yaqoob and Mengbing Huang, “Lattice-site-specific diffusion for substitutional and interstitial impurity atoms in ZnO crystals”, Journal of Applied Physics 120, 115102 (2016).
- Faisal Yaqoob and Mengbing Huang, “Effects of high-dose hydrogen implantation on defect formation and dopant diffusion in silver implanted ZnO crystals”, Journal of Applied Physics 120, 045101 (2016).
- Natasha Tabassum, Vasileios Nikas, Brian Ford, Mengbing Huang, Alain E. Kaloyeros and Spyros Gallis, “Time-resolved analysis of the white photoluminescence from chemically synthesized SiCxOy thin films and nanowires”, Applied Physics Letters 109, 043104 (2016).
- Perveen Akhter, Mengbing Huang, William Spratt, Nirag Kadakia and Faisal Amir, “Tailoring the optical constants in single-crystal silicon with embedded silver nanostructures for advanced silicon photonics applications”, Journal of Applied Physics 117, 123102 (2015).