Journal ~f Applied Spectroscopy. V~d. 67. No. 2. 2000 PHOTOLUMINESCENCE OF AgGaTe2 SINGLE CRYSTALS I. V. Bodnar', a* V. F. Gremenok, b R. V. Martin, c O. N. Obraztsova, a M. V. Yakushev, a A. E. Hill, d R. D. PUkington, a and R. D. Thomlinson a UDC 539.216.2535 The temperature dependence of the phomluminescence spectra of AgGaTe2 single crystals obtained by the Bridgman-Stockbarger method is investigated within the temperature range 10-300 K. The emission bands associated with donor-acceptor recombination and .fi'ee and bound ercitons are detected. The bonding energy of the .fi'ee ~:vciton and the forbidden gap of the crystals at 10 K are calculated. Keywords: photoluminescence, exciton, forbidden gap, chulcopyrite semicomluctors. Introduction. The compound AgGaTe 2 is a typical representative of the ternary semiconductor com- pounds I-III-VL with the chalcopyrite structure [1]. The presence of direct band-to-band transitions and the birefringence in the crystals of these compounds makes them promising for manufacturing highly efficient pho- toconverters [2], electrooptical modulators, narrow-band filters in the visible and IR spectral ranges, and other devices I3-5]. The ternary compound AgGaTe 2 is the least studied in the group of I-III-VI, compounds because of the technological difficulties encountered in growing high-quality crystals. In [6-8], the data on investigations of the electrical and optical properties of this compound are reported. At the same time successful practical implementation of the advantages of the semiconductor material mentioned calls for knowledge of its funda- mental parameters. The aim of the present work is to investigate the low-temperature photoluminescence (PL) of AgGaTe 2. Experimental. Synthesis and growth of AgGaTe 2 single crystals from elemental components were car- ried out in evacuated double quartz ampoules. Alter the synthesis in a one-zone furnace the ampoule was placed into a vertical two-zone furnace, in which single crystals were grown by the Bridgman-Stockbarger method. The melt zone was maintained at a temperature of -1040 K, and the annealing zone at 880 K. The melt was kept under these conditions for 24 h, then the anapoule with the melt was allowed to run through the crystallization zone at 0.12 mm/h with the temperature gradient -40 K/cm. The single crystals obtained under such conditions were of diameter 12 mm and length 40 ram, and were homogeneous over the entire length of an ingot, as established by x-ray microspectral and x-ray analysis. A quantitative elementary analysis of the grown AgGaTe 2 single crystals was carried out on a scanning electronic macroscope, model JSM-6400, with precision of +5%. The results of the analysis show that the com- position of the samples investigated is [Ag]:[Gal:[Te] = 25.62:24.36:50.02. No essential deviations in the com- position are observed at different points, which is indicative of the homogeneity of the samples. The state of equilibrium and the structure of the AgGaTe~ crystals were established by the x-ray method using a CuK a *To whom correspondence should be addressed. aBelarusian State University of Inlormation Science and Radioelectronics, 6 P. Brovka Str., Minsk, 220027, Belarus; e-mail: cit@micro.rei.minsk.by; OInstitute of the Solid-State and Semiconductor Physics of the National Academy of Sciences of Belarus, Minsk, Belarus; CStratclyde University, Department of Physics and Applied Phyics, Glasgow G40NG, Great Britain; '~Salford University, Salford M5 4WT, Great Britain. Trans- lated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 2, pp. 222-224, March-April, 2000. Original article submitted March 1, 1999. 0021-9037/00/6702-0303525.00 @2000 Kluwer Academic/Plenum Publishers 303