CVT-GROWTH OF AGGASE2 SINGLE-CRYSTALS - ELECTRICAL AND PHOTOLUMINESCENCE PROPERTIES

Single crystals of AgGaSe2 were grown by the Chemical Vapor Transport (CVT) -method using iodine as transport agent. Growth temperatures of 770 degrees C and concentrations of the transport agent of 1.6-1.7 mg I-2/cm(3) yielded compact single crystals with a size of up to 8 x 5 x 5 mm(3) and a habitus dominated by the {112}-faces. The as-grown crys tals were highly insulating (sigma < 10(-8) (Omega cm)(-1)). Annealing of the crystals in vacuum at 700 degrees C resulted in n-type conduct ivity of 2.10(-1) (Omega cm)(-1) with a dominant peak in the photolumi nescence spectra at 4 K associated with a donor level of 164 meV. Anne aling in Se-atmosphere at 600 degrees C lead to p-type conductivity of 6.10(-6) (Omega cm)(-1) within a surface layer of the AgGaSe2 single crystals. The corresponding photoluminescence spectra and the activati on energy of the electrical conductivity (between 100 K and 300 K) sug gest the presence of an acceptor (V-cation) with an activation energy of 60 meV and a donor (V-Se) with an activation energy of 100 meV.