John Emerson Ayers Ph.D.
Our broad area of research is the growth and characterization of semiconductor materials and devices.Specific focus areas include the following:
* Mismatched heteroepitaxy of semiconductors using non-compliant substrates and patterned heteroepitaxial processing. We have a United States patent pending for the patterned heteroepitaxial process.
* Compliant substrates and mismatched heteroepitaxy. The use of compliant substrates and patterned heteroepitaxy appear to be complimentary techniques. Compliant substrates are the best approach for mismatch up to about 1% and for smaller diameter wafers; patterned heteroepitaxial processing appears to be a better approach for larger wafers or f > 1%.
* MOVPE growth of zinc-free II-VI materials and heteroestuctures for blue LED's and laser diodes. The zinc-free II-VI materials, such as BeMgSeTe and BeCdSeTe, are an interesting alternative to the traditional materials systems based on GaN or ZnSe. The beryllium-based II-VI's exhibit robustness comparable or better than GaN but can be lattice-matched to GaAs like ZnMgSSe.
* Modeling of threading dislocation densities in mismatched heteroepitaxial layers. Much is known regarding region I (pseudomorphic layers) and the critical layer thickness. We have studied the threading dislocation densities in region III (h >> hc) and have developed the glide model which accurately predicts the thickness and mismatch dependencies of threading dislocation densities in mismatched heteroepitaxial layers. Currently we are trying to understand and model the behavior in region II (hc < h < 10hc), for which the threading dislocation density first increases, and then begins to decrease.
* MOVPE growth and characterization of ZnCdSe, ZnSSe, ZnMgSSe, and ZnMgSSe/ZnCdSe/ZnMgSSe quantum well devices.
EducationB.S., Electrical Engineering, University of Maine, 1984; M.S., Electrical Engineering, Rensselaer Polytechnic Institute, 1987; Ph.D., Electrical Engineering, Rensselaer Polytechnic Institute, 1990.
Institute of Electrical and Electronics Engineers (IEEE); Materials Research Society (MRS); American Crystallographic Association (ACA); American Physical Society (APS).
Editor, IEEE Transactions on Electron Devices.
Session Chair, Optics East, Philadelphia, Pennsylvania, October, 2004.
Member, Program Committee, Nano-Sensors and Devices, Optics East, Boston, MA, 2005.
Member, Program Committee, Nano Integrations, Optics East, Boston, MA, 2005.
Panel Reviewer, National Science Foundation, December, 2004.
Chair, National Science Foundation Review Panel, June, 2005.
By this Researcher