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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 4 — Feb. 15, 2010
  • pp: 3820–3827

Polarized-thermoreflectance study of the band-edge transitions in Cu(Al0.5In0.5)S2 solar-energy related crystal

Ching-Hwa Ho and Guan-Tzu Huang  »View Author Affiliations

Optics Express, Vol. 18, Issue 4, pp. 3820-3827 (2010)

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Polarization dependence of band-edge excitonic transitions in Cu(Al0.5In0.5)S2 [denoted as Cu(AlIn)S2] has been characterized using polarized-thermoreflectance (PTR) measurements with E || <11 1 ¯ > and E ⊥ <11 1 ¯ > polarizations in the temperature range between 30 and 320 K. The measurements were done on as-grown {112} surface of the chalcopyrite crystal. The polarization dependence of the band-edge transitions of Cu(AlIn)S2 clearly showed that the EA exciton is present prominently with E || <11 1 ¯ > polarization while the EB exciton appears significantly only in the E ⊥ <11 1 ¯ > polarized spectra. For the unpolarized spectra, both EA and EB features were combined. The EA feature is closely related to the E0 transition, while the EB feature is that of E0 + Δ0 transition in the chalcopyrite. The crystal-field splitting energy of Δ0 of Cu(AlIn)S2 at the valence-band top is determined accurately by PTR experiments. Temperature dependences of transition energies of EA and EB transitions were analyzed. The band-edge excitons reveal an anomalous temperature-energy shift with increasing the temperatures from 30 to 320 K due to the variation of Cu d electrons’ contribution to valence band that affected by the native defects inside Cu(AlIn)S2. The PTR technique is more effective in studying the band-edge structure of the chalcopyrite crystal.

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OCIS Codes
(160.4760) Materials : Optical properties
(160.6000) Materials : Semiconductor materials
(300.6380) Spectroscopy : Spectroscopy, modulation
(300.6470) Spectroscopy : Spectroscopy, semiconductors

ToC Category:

Original Manuscript: October 16, 2009
Revised Manuscript: February 8, 2010
Manuscript Accepted: February 9, 2010
Published: February 11, 2010

Ching-Hwa Ho and Guan-Tzu Huang, "Polarized-thermoreflectance study of the band-edge transitions in Cu(Al0.5In0.5)S2 solar-energy related crystal," Opt. Express 18, 3820-3827 (2010)

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