Determination of the optical energy gap of Ge_1–xSn_x alloys at 4K

 

H. Pérez Ladrón de Guevara¹, A. G. Rodríguez², H. Navarro–Contreras², and M. A. Vidal²

 

Universidad de Guadalajara–Centro Universitario de los Lagos Enrique Díaz de León s/n col. Paseo de la Montaña, Lagos de Moreno, Jal. 47460.

Instituto de Investigación en Comunicación Óptica (IICO), Universidad Autónoma de San Luís Potosí Álvaro Obregón 64, San Luís Potosí, S.L.P. 78000

 

Recibido: 15 de diciembre de 2007.
Aceptado: 9 de abril de 2008.

 

Abstract

The optical energy gap of Ge_1–xSn_x alloys (x < 0.14) has been determined from transmittance measurements at 4K using a Fast–Fourier–Transform Infrared Interferometer (FFT–IR) attached to a helium refrigerator. Our results show that the energy gap changes due to the Sn concentration of the alloys. We also show that low temperature increases the energy gap transitions for alloys with low Sn concentrations. By increasing gradually the Sn concentration in alloys the energy gaps decreases, but for x>0.13 alloys, direct energy gap transitions are lower than energy gap obtained at room temperature. These results are according to the theory predicted results at low temperatures.

Keywords: Sputtering; FFT–IR; HRXRD.

 

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