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Dr. Axel Scherer Bernard A. Neches Professor of Electrical Engineering, Applied Physics, and Physics; Co-Director, Kavli Nanoscience Institute 203
Sloan Annex B.S.
- New Mexico Tech, 1981 |
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Field of Study Today, we can produce structures with lateral sizes as small as 6 nm by combining electron beam lithography and dry etching. Dr. Scherer's research laboratory is built around producing such nanostructures and applying them to new optelectonic, magneto-optic and high-speed electronic devices. The aim of his research group is to develop functional devices which use their reduced geometries to obtain higher speed, greater efficiencies, and can be integrated into systems in large numbers. Successful integration of such devices in large numbers requires detailed understanding and optimization of both the individual processing steps as well as the device performance. The evolution of vertical cavity surface emitting lasers is one example of such device development. This laser structure, due to its unique geometry, allows integration of large numbers of devices in a relatively small area. Although high threshold currents and voltages still limit the integration of large numbers of devices, the performance of these devices has recently been dramatically improved. This development of efficient discrete lasers, and their subsequent integration into large systems is possible as a result of careful design, fabrication, and packaging. Dr. Scherer's group expects to continue to develop such new systems, and generate technology which can directly be transferred to industry for commercialization. The second research thrust involves observing new and interesting geometry-dependent physical phenomena in artificial microstructures. The development of a microfabricated optical crystal which reflects light in all directions at a particular wavelength is one such application. this structure, which is called a photonic bandgap crystal, requires angle etching of deep 300 nm holes to simulate a face centered cubic lattice of holes in a semiconductor. The resulting artificial microfabricated material, if used ion a laser structure, can significantly improve the laser efficiency by virtually eliminating any light lost due to scattering. Similarly to a semiconductor crystal with a bandgap, defects in a photonic bandgap crystal give rise to acceptor and donor modes, which can also be described as three-dimensional optical microresonators. The third research thrust of Dr. Scherer's group pushes the limits of lithography and pattern transfer to the absolute limit. By using conventional electron beam lithography and etching techniques, structures with lateral sizes of 30 nm are typically obtained. However, these sizes can be significantly reduced, and structures as small as 6 nm have been fabricated in semiconductor material. This requires not only high resolution lithography, but also the ability to anisotropically transfer the mask patterns into the material of interest, without disrupting the properties of that material through ion damage or oxidation. Applications for such nanofabrication lie in new magnetic structures, as well as quantum structures used to explore single electron tunneling effect. Dr. Scherer is professor of electrical engineering, applied physics, and physics, specializing in device microfabrication and packaging. He graduated form New Mexico Institute of Mining and Technology in 1985, and has worked in the Quantum Device Fabrication group at Bellcore for the following 8 years. In the past, Dr. Scherer has specialized on improving the state of the art of semiconductor microfabrication, which resulted in the development of the smallest vertical cavity lasers (400 nm wide), some of the world's smallest etched structures (6 nm wide) as well as ultra-narrow gratings (30 nm pitch). He has also been working on reducing the sizes of microlasers and changing their emission wavelengths. The equipment available in Dr. Scherer's fabrication facility includes a high voltage scanning transmission electron microscope and several scanning electron microscopes for high resolution pattern definition. Pattern transfer techniques which are used to define nanostructures include reactive ion beam, reactive ion and chemically assisted ion beam etching systems. The laboratory also uses a focused ion beam etching system for maskless pattern transfer. Since most of this instrumentation is not commercially available, it is home-built. building and maintenance of such state of the art equipment also gives students an excellent opportunity for gaining first-hand insight and expertise in the design of modern fabrication equipment. Selected Publications A. Scherer, J.L. Jewell, M. Walther, J.P. Harbison, L.T. Florez, "Fabrication of low threshold voltage microlasers", Electronics Letters, 28, pp. 1224. A. Scherer, M. Walther, L.M. Schiavone, B.P. Van der Gaag, E.D. Beebe, "High reflectivity dielectric mirror deposition by reactive magnetron sputtering", J. Vac. Sci. Technol., (in print, 1992) A. Scherer, J.L. Jewell, J.P., "Harbison: Lasing in sub-micron wide vertical cavity microlasers, Optics and Photonics News", vol 2, pp. 9, (1991) J.L. Jewell, J.P. Harbison, A. Scherer, "Microlasers", Scientific American, pp. 86, November (1991) A. Scherer, B.P. Ban der Gaag, "Characterization of nanostructures by reflection electron microscopy", Appl. Phys. Lett., 56, pp. 2566, (1990) |
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