Photoluminescence investigation of the indirect band gap and shallow impurities in icosahedral B[subscript]12As[subscript]2

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Show simple item record Klein, P. B. Nwagwu, Ugochukwu Edgar, James H. Freitas, J. A., Jr. 2012-09-07T18:51:03Z 2012-09-07T18:51:03Z 2012-09-07
dc.description.abstract The indirect band gap of icosahedral B[subscript]12As[subscript]2 (IBA) has been determined by variable temperature photoluminescence measurements (8 K-294 K) on solution-grown bulk samples. In addition, evidence of three shallow acceptor levels and one shallow donor level is reported. The low-temperature spectra were characterized by broad and intense deep defect emission, donor-acceptor pair (DAP) bands, and exciton recombination. The appearance of DAP emission verifies the incorporation of a donor in IBA, which has not been reported previously. The temperature dependence of the free exciton (FE) intensity reflected a FE binding energy of 45 meV. The variation of the FE peak position with temperature was fitted with both Varshni and Pässler models to determine an expression for the temperature dependence of the indirect band gap. The resulting low and room temperature band gaps are E[subscript]g(0) = 3.470 eV and E[subscript]g(294 K) = 3.373 eV, respectively. The latter is not consistent with previous reports of the room temperature band gap, 3.20 eV and 3.47 eV, derived from band structure calculations and optical absorption, respectively. The origin of these discrepancies is discussed. The DAP spectra reveal three relatively shallow acceptors with binding energies of ≈175, 255, and 291 meV, and a shallow donor with binding energy ≈25 meV. Although the identity of the individual acceptors is not known, they appear to be associated with the light-hole band. The small donor binding energy is suggestive of an interstitial donor impurity, which is suspected to be Ni. en_US
dc.relation.uri en_US
dc.rights Copyright 2012 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. en_US
dc.subject Photoluminescence en_US
dc.subject Icosahedral B12As2 en_US
dc.subject Indirect band gap en_US
dc.title Photoluminescence investigation of the indirect band gap and shallow impurities in icosahedral B[subscript]12As[subscript]2 en_US
dc.type Article (publisher version) en_US 2012 en_US
dc.citation.doi doi:10.1063/1.4729920 en_US
dc.citation.epage 013508-12 en_US
dc.citation.jtitle Journal of Applied Physics en_US
dc.citation.spage 013508-1 en_US
dc.citation.volume 112 en_US
dc.contributor.authoreid edgarjh, d0444080 en_US

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