Good quality, large single crystals of CdSe were grown by the modified growth method (i.e., vertical unseeded vapor phase growth with multi-step purification of the starting material in the same quartz ampoule without any manual transfer between the steps). Lower temperature gradients (8-9degreesC cm) at the growth interface were used for the crystal growth, As-grown CdSe crystals was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive analyzer of X-rays, high-resistance instrument measurement, and etch-pit observation, It is found that there are two cleavage faces of (1 0 0) and (1 1 0) orientations on the crystal, the resistivity is about 10(8) Omega cm. and the density of etch pits is about 10(3-4), cm(2). The crystal,vas cut into wafers and was fabricated into detectors, The detectors were tested using an Am-241 radiation source. gamma-ray spectra at 59.5 keV were obtained. The results demonstrated that the quality of the as-grown crystals was good. The crystals were useful for fabrication of room-temperature-operating nuclear radiation detectors. Therefore, the modified growth technique is a promising, convenient, new method for the growth of high-quality CdSe single crystals. (C) 2002 Elsevier Science B.V. All rights reserved.