Person:

Doolittle, William Alan

Permanent Link

https://hdl.handle.net/1853/71222

Associated Organization(s)

Organizational Unit

School of Electrical and Computer Engineering

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Now showing 1 - 9 of 9

Creative Epitaxy: Finding Ways to Violate Assumptions that Breach Material Barriers

(Georgia Institute of Technology, 2022-01-11) Doolittle, William Alan

Epitaxial processes are considered routine for applications spanning established industries from the silicon and GaN semiconductor industries to cutting edge research. As many as 10,000 epitaxial reactors crank out billions of dollars’ worth of light emitting diode chips for solid state white lighting alone. Those metrics increase 100-fold for silicon applications. Epitaxy is core to countless industries but is mostly performed in ways that have not changed for decades. But epitaxy can also be performed in non-standard ways to overcome “perceived” barriers to materials synthesis. Several examples will be given in this talk including: 1) Dynamic control of surface chemistry so as to enable higher solubility of desirable impurities; 2) Dynamic control of surface energy facilitating 3D control of alloy composition and material properties; 3) Electrothermal control of epitaxy to enable metastable phase materials; and 4) the “invention” of the widest semiconductor known. Each of these example problems has been solved by a common “thought process” wherein the fundamental assumption behind the limitation was defined and ways of violating the identified assumption was explored leading to new functionality in materials. The importance of the process – assumption identification and violation – will be discussed in hopes of conveying an important approach to solving hard problems. New emerging industries such as optoelectronics, neuromorphic computing and power electronics will be highlighted as beneficiaries of these unique approaches.
Multiferroic materials for microwave parametric power amplifiers

(Georgia Institute of Technology, 2011-05-15) Kenney, J. Stevenson ; Doolittle, William Alan ; Papapolymerou, Ioannis John
ARO DURIP report - custom scanning tunneling microscope

(Georgia Institute of Technology, 2011-01-18) Doolittle, William Alan
CAREER: New device opportunities enabled by polar dielectric and semiconductor heteroepitaxy

(Georgia Institute of Technology, 2009-03-31) Doolittle, William Alan ; Lee, Kyoung-Keun Lee
Heat dissipation in high-power GaN electronics on thermally resistive substrates

(Georgia Institute of Technology, 2005-08) Christensen, Adam ; Doolittle, William Alan ; Graham, Samuel

The heat dissipation in GaN devices grown on low thermal conductivity lithium gallate (LGO) substrates was investigated. The thermal conductivity of single-crystal LGO was measured utilizing the 3ω technique for temperatures ranging from 100 K–500 K. For the GaN layer, the thermal conductivity was estimated using a phonon transport model which included dislocation density and temperature dependence. These data were then used in a finite element program to determine the thermal behavior of a heterojunction field-effect transistor. Based on a maximum junction temperature of 500 K, it was found that devices with a power dissipation of 1W/mm were possible if the primary heat dissipation path was through the low thermal conductivity substrate. However, in using a front side cooling scheme, results suggest that it may be possible to develop devices with power dissipation in the range of 10 W/mm.
Leaky surface acoustic waves in Z-LiNbO ₃ substrates with epitaxial AlN overlays

(Georgia Institute of Technology, 2004-10) Bu, G. ; Ciplys, D. ; Shur, M. S. ; Namkoong, G. ; Doolittle, William Alan ; Hunt, William D.

The properties of leaky surface acoustic waves (LSAW) in MBE grown AIN layer on Z-cut LiNbO₃ structures have been studied by numerical simulation and experimental measurements and compared with those of Rayleigh waves in the same structure. In the range of AIN layer thicknesses studied (0
Novel High Efficiency Photovoltaic Devices Based on the III-N Material System

(Georgia Institute of Technology, 2004-06-08) Doolittle, William Alan
Applied EPI RF matching network final report

(Georgia Institute of Technology, 2004-03-31) Doolittle, William Alan
Fundamental understanding, characterization, passivation and gettering of electrically active defects in silicon

(Georgia Institute of Technology, 1996-05) Doolittle, William Alan