Pool-Frenkel thermoelectric modulation of exciton photoluminescence in GaSe crystals

Effect of external field on the exciton photoluminescence of GaSe crystals has been investigated and it has been observed that the PL is quenched with the applied field. The changes observed in the PL spectra have been analyzed with impact exciton, Franz-Keldysh and Pool-Frenkel effects. From the analyses of the experimental data, it has been found that the intensity of direct free, indirect free and bound exciton peaks decreased exponentially with the square root of applied field as I∼exp-β√E. The energy positions of emission peaks were found to shift to longer wavelength with the applied field as ΔE∼β√E. From these findings, the Pool-Frenkel thermoelectric field effect is seen to be the dominant mechanism in the variation of exciton PL with the applied field even though the impact exciton and Franz-Keldysh effects contribute.

► Exciton PL intensity varies with the applied field. It decreases with the square root of E in accordance with Pool-Frenkel effect. ► In the intrinsic region of PL spectrum, lines belonging to direct and indirect free/bound excitons were observed. ► Line positions shifted to longer wavelengths with the applied field. ► It was shown that amplitude modulation of exciton PL with electric field was possible.