LUMINESCENT AND PHOTOCONDUCTIVE PROPERTIES OF AGGA2.5IN2.5S8 AND CUGA2.5IN2.5S8 NEW SEMICONDUCTORS

Results of a complex study of photoluminescence (PL), photoconductivit y (PC) and photo-voltaic (PV) spectra in AgGa2.5In2.5S8 and CuGa2.5In2 .5S8 single crystals are presented. The values of indirect (E(g)i = 2. 25 eV) and direct (E(g)d = 2.60 eV, T = 300 K) gaps in AgGa2.5In2.5S8 have been determined. PL spectrum of AgGa2.5In2.5S8 is shown to consis t of two overlapping bands with the maxima at 1.57 and 1.95 eV (T = 77 K), while CuGa2.5In2.5S8 is characterized by a single PL band, the po sition of its maximum (1.72-1.77 eV) depending upon the excitation pow er density. The radiative electron transitions in CuGa2.5In2.5S8 are a ssumed to occur from the quasicontinuously distributed traps below the bottom of the conduction band to an acceptor level with 0.07 eV activ ation energy.