The electric‐field effect on the exciton photoconductivity and Urbach tail in GaSe crystals

Abstract

AbstractThe direct free exciton (n = 1) photoconductivity in GaSe crystals has been investigated as a function of applied electric field. The changes observed in the exciton photoconductivity have been analyzed using the Franz–Keldysh, exciton electroabsorption, and Frenkel thermoelectric‐field effects. The intensity of exciton photoconductivity peak was found to increase exponentially with the applied field. The exciton peaks broaden as the magnitude of applied field is increased and shift to lower energies with the square root of applied field. The Urbach energy determined from the long‐wavelength part of the exciton photoconductivity in GaSe crystals varies with the applied electric field. The Frenkel thermoelectric‐field effect has been found to be dominant for the changes observed in the exciton photoconductivity as a result of the applied field. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)