Exploring Ultimate Limits of Energy Dissipation in Wide-Bandgap Semiconductors
Abstract
Investigate the fundamental limits of energy dissipation processes in wide-bandgap semiconductors GaN and SiC, focusing on the unsolved fundamental questions: how do coherent waves decay in these crystal structures, how does energy transfer between phonon modes and thermal effects in the crystal lattices, how does energy dissipate at the boundaries of thin layers of these and other materials, and what are possible solutions for achieving high quality factors in devices based on these materials? Also, following preliminary indications, is it possible to achieve phonon gain in bulk acoustic wave (BAW) structures? First, take an integrative Ômaterials-of-designÕ approach in the research by combining materials with functional devices. The devices used will be M/NEMS resonators, but the loss issues will apply to a wide range of device structures. These devices are expected to be the most suitable for probing certain energy dissipation channels. Second, focus on the wide-bandgap materials (GaN, SiC), grown by MBE, MOCVD, and APCVD (Atmospheric pressure CVD), that are of increasing importance for these and other device applications Ð because these crystalline materials offer very rich and unique Ômulti-lateralÕ coupling effects between electronic, phononic, and photonic domains. Exploit such coupling effects to explore fundamental energy dissipative processes, all the way down to atomic levels, by using ultrasensitive electronic and optical measurement techniques that would help capture signatures of mesoscopic energy dissipation events. Optical interferometric microspectroscopy, RF frequency response, and RF time-domain ring down will be used to measure the dissipation (Q or quality factor) of the resonance, with photoluminescence, ultra-high-resolution SEM, and x-ray electron dispersive spectroscopy used to characterize the fundamental materials properties. Extrinsic loss mechanisms will be suppressed. Support loss will be reduced using phononic crystals and phonon trapping. Air damping and thermoelastic damping will be suppressed by operating the resonators at cryogenic temperatures. Surface losses will be minimized using previously demonstrated nano-fabrication techniques to build resonators with vertically smooth sidewalls and surfaces. The various intrinsic loss mechanisms will be explored by deconvolving their different dependences on temperature and electric field. Focus, in particular, on quantifying and approaching the fundamental limits of electron-phonon and phonon-phonon interactions, and thermoelastic dissipations. The revelation of the ultimate limits of these intrinsic energy losses will further be applied to specific devices for validation of the underlying principles.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 06, 2017
- Source ID
- W911NF1610340
Entities
People
- Mina Raieszadeh
Organizations
- Army Contracting Command
- United States Army
- University of Michigan