Photoluminescence of glassy and single-crystalline GeSe2 measured at 77K

Photoluminescence (PL) and excitation (E) spectra of glassy and crystalline GeSe₂ at 77 K have a broad-band peaked at energy $\text{E}{}_{\mathrm{R}}\text{<}\text{1}\text{2}\text{E}{}_{\mathrm{g}}$. PL spectra have a Gaussian form: the Stokes shift (W_S=?ω?E_R) for crystalline GeSe₂ is greater than that for the glass. The absorption coefficient α at the maxima of E spectra is ～ 10²cm^-1 for the glassy form, and ～ 10⁴cm^-1 for the crystalline form. The results are interpreted in terms of the Mott-Davis-Street model supposing a strong electron-phonon coupling in these types of amorphous semiconductors which explains the large Stokes shift and the broad emission band.