NATURE OF ENERGY-BANDS OF AIIIBVI LAYERED CRYSTALS NEAR THE ABSORPTION-EDGE

Transmission and photoluminescence spectra are investigated of GaSe1−xTex and Ga1−xInxSe crystals in the temperature range 4.2 to 100 K. It is shown that low temperature radiative recombination in these crystal is mainly due to direct bound exciton decay. In the temperature range 10 K < T < 77 K radiative recombination has an impurity character, and at T = 77 K direct free exciton radiative recombination takes place. The examination of direct exciton zone behaviour when substituting the anions Te, S for Se in GaSe (Se → Te, S) and cations (Ga → In) allows to conclude, that the anions make the major contribution to the formation of electronic states at the direct absorption edge of GaSe and its analogs. It is shown that the bottom of the conduction band at the edge of Brillouin zone of the investigated crystals is formed with considerable participation of cations. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA