Publications by Year: 2018

2018
Defo, Rodrick Kuate, Xingyu Zhang, David Bracher, Gunn Kim, Evelyn Hu, and Efthimios Kaxiras. 2018. “Energetics and kinetics of vacancy defects in 4H-SiC.” Physical Review B 98 (10): 104103. Abstract
Defect engineering in wide-gap semiconductors is important in controlling the performance of single-photon emitter devices. The effective incorporation of defects depends strongly on the ability to control their formation and location, as well as to mitigate attendant damage to the material. In this study, we combine density functional theory, molecular dyamics (MD), and kinetic Monte Carlo (KMC) simulations to study the energetics and kinetics of the silicon monovacancy VSi and related defects in 4H-SiC. We obtain the defect formation energy for VSi in various charge states and use MD simulations to model the ion implantation process for creating defects. We also study the effects of high-temperature annealing on defect position and stability using KMC and analytical models. Using a larger (480-atom) supercell than previous studies, we obtain the temperature-dependent diffusivity of VSi in various charge states and find significantly lower barriers to diffusion than previous estimates. In addition, we examine the recombination with interstitial Si and conversion of VSi into CSiVC during annealing and propose methods for using strain to reduce changes in defect concentrations. Our results provide guidance for experimental efforts to control the position and density of VSi defects within devices, helping to realize their potential as solid-state qubits.
Wang, Danqing, Tongtong Zhu, Rachel A. Oliver, and Evelyn L. Hu. 2018. “Ultra-low-threshold InGaN/GaN quantum dot micro-ring lasers.” Optics Letters 43 (4): 799-802. Publisher's Version
Greenspon, Andrew S., Brandt L Marceaux, and Evelyn L. Hu. 2018. “Robust lanthanide emitters in polyelectrolyte thin films for photonic applications.” Nanotechnology 29 (7): 075302. Publisher's Version Abstract
Trivalent lanthanides provide stable emission sources at wavelengths spanning the ultraviolet through the near infrared with uses in telecommunications, lighting, and biological sensing and imaging. We describe a method for incorporating an organometallic lanthanide complex within polyelectrolyte multilayers, producing uniform, optically active thin films on a variety of substrates. These films demonstrate excellent emission with narrow linewidths, stable over a period of months, even when bound to metal substrates. Utilizing different lanthanides such as europium and terbium, we are able to easily tune the resulting wavelength of emission of the thin film. These results demonstrate the suitability of this platform as a thin film emitter source for a variety of photonic applications such as waveguides, optical cavities, and sensors.