Ultra-low values of the absorption coefficient for band–band transitions in moderately doped Si obtained from luminescence
1996; American Institute of Physics; Volume: 80; Issue: 9 Linguagem: Inglês
10.1063/1.363471
ISSN1520-8850
Autores Tópico(s)Silicon and Solar Cell Technologies
ResumoThe absolute value of the absorption coefficient αbb(ℏω) for band–band transitions near the band edge was determined in moderately doped silicon by photoluminescence spectra analysis. The major advantage of this method in determining αbb(ℏω) is the lack of interference with free carrier absorption, in contrast to conventional methods like transmission or photothermal deflection measurements. We deduce values for αbb(ℏω), which are nearly five orders of magnitude smaller than the absorption coefficient αfc(ℏω) for free carrier absorption. With this method it is possible to examine in detail the influence of doping on the absorption coefficient for band–band transitions near the absorption edge. The appearance of band tails and band-gap narrowing are very well reflected. With conventional methods, which can only detect the overall absorption of the incident radiation, the determination of αbb(ℏω) in the vicinity of the band edge is impossible for moderately and heavily doped silicon, because it is completely masked by the free carrier absorption.
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