Randall Feenstra Professor Ph.D., California Institute of Technology Email: feenstra@andrew.cmu.edu Phone: (412) 268-6961 Fax: (412) 681-0648

The research activities of my group deal with structural and electronic properties of semiconductor materials and devices. The major tool used in the studies is the scanning tunneling microscope, which allows one to image the atomic structure of a surface and to perform spectroscopic measurements of the electronic energy levels. Studies performed in the past include atom specific imaging of different chemical species on a surface, and observations of atomic diffusion leading to surface phase transitions at elevated temperature. More recently, we have studied semiconductor heterostructures consisting of multiple layers of different types of material, with the goal of understanding how the structure of the device (including imperfections and defects) determines its electronic properties. 

Growth of semiconductor heterostructures is performed in my laboratory using molecular beam epitaxy. We have concentrated on the growth of GaN, a semiconductor with a relatively large band gap used for blue light-emitting devices and for microwave transistor applications. Our focus is surface studies of the GaN films. From studies of the surface reconstructions we have deduced mechanisms for film growth and for incorporation of various species such as In, Si, and Mg used in doping and alloy formation.

Description of research, and publications, in Prof. Feenstra's group.

Selected Publications

R. M. Feenstra, Y. Dong, M. P. Semtsiv, and W. T. Masselink, “Influence of Tip-induced Band Bending on Tunneling Spectra of Semiconductor Surfaces”, Nanotechnology 18, 044015 (2007).

Y. Dong, R. M. Feenstra and J. E. Northrup, “Electronic States of Oxidized GaN(0001) Surfaces”, Appl. Phys. Lett. 89, 171920 (2006).

S. Nie and R. M. Feenstra, “Scanning Tunneling Spectroscopy of Oxidized 6H-SiC Surfaces”, Mater. Sci. Forum  527-529, 1023 (2006).

R. M. Feenstra, S. Gaan, G. Meyer and K. H. Rieder, “Low-temperature Tunneling Spectroscopy of Ge(111)c(2x8) surfaces”, Phys. Rev. B 71, 125316 (2005).

Y. Dong, R. M. Feenstra, D. W. Greve, J. C. Moore, M. D. Sievert, and A. A. Baski, “Effects of Hydrogen on the Morphology and Electrical Properties of GaN grown by Plasma-assisted Molecular Beam Epitaxy”,  Appl. Phys. Lett. 86, 121914 (2005).