Randall Feenstra

Professor, Physics

Education

Research

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

• N. Srivastava, Guowei He, Luxmi, R. M. Feenstra, Interface structure of graphene on SiC(0001̅), Physical Review B 85, 041404 (2012)
• G. Bussetti et al., Coexistence of Negatively and Positively Buckled Isomers on n⁺-Doped Si(111)-2×1, Physical Review Letters 106, 067601 (2011)
• Luxmi, N. Srivastava, Guowei He, R. M. Feenstra, P. J. Fisher, Comparison of graphene formation on C-face and Si-face SiC {0001} surfaces, Physical Review B 82, 235406 (2010)
• Luxmi, P. J. Fisher, N. Srivastava, R. M. Feenstra, Yugang Sun, J. Kedzierski, P. Healey, Gong Gu, Morphology of graphene on SiC(0001) surfaces, Applied Physics Letters 95, 073101 (2009)
• Luxmi, Shu Nie, P.J. Fisher, R.M. Feenstra, Gong Gu, Yugang Sun, Temperature Dependence of Epitaxial Graphene Formation on SiC(0001), Journal of Electronic Materials 38, 718 (2009)
• Gong Gu, Shu Nie, R. M. Feenstra, R. P. Devaty, W. J. Choyke, Winston K. Chan, Michael G. Kane, Field effect in epitaxial graphene on a silicon carbide substrate, Applied Physics Letters 90, 253507 (2007)
• Y. Dong, R. M. Feenstra, D. W. Greve, J. C. Moore, M. D. Sievert, A. A. Baski, Effects of hydrogen on the morphology and electrical properties of GaN grown by plasma-assisted molecular-beam epitaxy, Applied Physics Letters 86, 121914 (2005)
• J. Neugebauer, T. K. Zywietz, M. Scheffler, J. E. Northrup, H. Chen, R. M. Feenstra, Adatom Kinetics On and Below the Surface: The Existence of a New Diffusion Channel, Physical Review Letters 90, 056101  (2003)
• C. D. Lee, Ashutosh Sagar, R. M. Feenstra, C. K. Inoki, T. S. Kuan, W. L. Sarney, L. Salamanca-Riba, Role of Ga flux in dislocation reduction in GaN films grown on SiC(0001), Applied Physics Letters 79, 3428 (2001)
• Huajie Chen, R. Feenstra, J. Northrup, T. Zywietz, J. Neugebauer, Spontaneous Formation of Indium-Rich Nanostructures on InGaN(0001) Surfaces, Physical Review Letters 85, 1902 (2000)
• A. R. Smith, R. M. Feenstra, D. W. Greve, M.-S. Shin, M. Skowronski, J. Neugebauer, J. E. Northrup, Determination of wurtzite GaN lattice polarity based on surface reconstruction, Applied Physics Letters 72, 2114 (1998)
• V. Ramachandran, M. F. Brady, A. R. Smith, R. M. Feenstra, D. W. Greve, Preparation of atomically flat surfaces on silicon carbide using hydrogen etching, Journal of Electronic Materials 27, 308 (1998)
• A. Smith, R. Feenstra, D. Greve, J. Neugebauer, J. Northrup, Reconstructions of the GaN(0001̅) Surface, Physical Review Letters 79, 3934 (1997)