A clarification of the optical interband transitions near the fundamental absorption edge of b-FeSi2

A. Glen Birdwell*, Deane Chandler-Horowitz, Tom Shaffner

Semiconductor Electronics Division, Electronics and Electrical Engineering Laboratory (EEEL), National Institute of Standards and Technology, Gaithersburg, MD 20899

S. Collins, R. Glosser

Department of Physics, University of Texas at Dallas, Richardson, Texas 75083

W. Henrion, M. Rebien, and P. Stauss

Hahn-Meitner-Institute, Department of Photovoltaics, Rudower Chaussee 5, D-12489 Berlin, Germany

A substantial research effort has been directed toward obtaining light emission from silicon-based materials for at least a decade. Achieving this goal would have an enormous impact on the computer and telecommunication industries if the technology could be made compatible with very large scale integrated processing and integration with optical fibers. Semiconducting silicides have recently gained significant interest as a possible route to obtaining this goal [1]. In particular, considerable excitement was created by the report of a light emitting diode based on ion beam synthesized (IBS) b-FeSi2 [2,3]. The device was fabricated by high dose ion implantation into a silicon substrate and was shown to produce 1.5 mm electroluminescence at room temperature. However, questions as to the origin of the luminescence still remain since significant light emission from b-FeSi2 grown by methods other than IBS has not been achieved. It is our view that these questions cannot be answered until the electronic and optical properties of this material are clarified. We will present results of photoreflectance spectroscopy of b-FeSi2 and will discuss the utility of this technique especially when applied to materials with complex electronic structure. Furthermore, we will show how photoreflectance can be used to resolve many of the troubling issues concerning light emission from IBSb-FeSi2.

[1] Semiconducting Silicides, edited by V. E. Borisenko, Springer Series in Material Science, p. 203 (Springer-Verlag, Berlin, 2000), Vol. 39.

[2] D. N. Leong, M. Harry, K. J. Reeson, and K. P. Homewood, Nature 387, 686 (1997).

[3] W. L. Ng, M. A. Lourenco, R. M. Gwilliam, S. Ledain, G. Shao, and K. P. Homewood, Nature 410, 192 (2001).

* National Research Council Postdoctoral Research Associate