抄録
Crystals of CuAlSe_2, one of the promising materials for optical or optoelectronic devices in blue color wavelength region, were grown by chemical vapor transport (CVT) method using iodine as a transport agent. An optimum condition for growth of large stoichiometric single crystals was determined by adjusting growth parameters such as an iodine concentration (D_1), source temperature (T_s), growth temperature (T_c) and temperature difference (ΔT) between T_s and T_c. A large single crystal with a well-developed (112) face with a typical dimension of 9×5×0.45mm^3 was obtained under the conditions of T_s =1223-1263K, ΔT=50K and D_I=2-3mg/cm^3. The transport rate in the present case is limitted by a condensation process of gas molecules in the vapor phase. Iodine with a concentration of several hundred ppm was found to be incorporated into crystals obtained. The incorporated iodine is expected to occupy mainly the Se site, a part of which occupies the nearest sites of Cu vacancy, forming the so-called S-A like complex center. Iodines which substitutes the Se site to form the complex center seem to affect the electrical and optical properties of grown crystals. Observed high p-type resistivity can be attributed to compensation of Cu-vacancy originated acceptor by iodine donor at the Se site. Two broad photoluminescence peaks observed at 1.82 and 1.96 eV was also related to the complex defects.
