Presented in this paper are the results obtained from the investigation of absorption edge and photoconductivity of layered Ga,In4S9 single crystals as well as from the investigation of the photovoltaic effect in Pt-Ga21n,Sp surface-barrier structures. We determined the magnitude of the direct band gap to be E, = 2.72 eV and the position of the sensitizing centres to be xO.15 eV above the valence band top. In the regions of the photon energies smaller than E, the absorption band edge is described by an exponential dependence with a temperature independent slope.

An investigation is made of the optical absorption, photoconductivity, and cathodoluminescence in CdIn2S2Se2 layered single crystals. The observed exponential absorption edge is explained as due to electron transitions from the valence tail states to the conductivity band. Direct allowed transitions are noticed at large absorption coefficients (> 104 cm−1). The band gap is equal to 2.10 eV at 300 K. Measurements of photoconductivity in crystals indicate a presence of photosensitive centres ≈ 1.55 eV below the conduction band bottom and a presence of sensitizing centres ≈ 0.13 eV above the valence band top. The recombination emission band of the CdIn2S2Se2 crystals is found to lie in the near infrared region 0.73 to 1.2 μm. Cathodoluminescence investigation data are in qualitative agreement with the model of the donor–acceptor pairs characteristic of which are smeared energy levels.

Single crystals of the HgGaInS, layered compound were grown by the iodine transport technique. Results of their optical, photoelectric, and radiative properties' study are presented. The band gap and the binding energy of holes on the sensitizing centres were determined to be E, = 2.41 eV and E. = 0.2eV, respectively. A presence of quasi-continuously distributed states was stated which are responsible for the exponential segment of the absorption edge and which take part in the radiative recombination. Bupawem MOHOKPHCTaTUIbI CnoHCTOrO coemeHHa H,GaInS, MeTOnOM XEIMIIgeCKRX TpaHc-IIOPTHX peaKuuii B ~~M K H Y T O~~iiorptwoii clicTeMe. IIpmeneHu pe3ynwam rrccnenosamia HX OnTHqecKm, + o~o m e~~p w e c~~x H ~3 n y q a~e m~~~ CBOECTB. OnpeneneHa mipma s a n p e q e~~o i i 30m E , = 2,413B, H 31iepr~x C B R~H WPOK Ha o9yBcrBnrwm qempax E, = 0,2 3B. YcraHoBneao rianHwe B sanpewe~~oii 3 o~e Ksa3menpepbmio pacnpeneneRwrx COCTOXH&, xoiopue 06ycno~m-m n y q a~e m~o i i pe~o~6rma~1.mi.BaWT IIpOTXXeHHLdi 3KClIOHeHuHaJIbHL& Y'iaclOK Kpaff IIOrJIO~eHHn li IIpHHHMaIoT paCTHe B