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Optical investigations of ZnSe crystals grown by the seeded vapour phase transport technique

The optical properties of ZnSe bulk crystals grown by the seeded physical vapour phase transport technique (SPVT) were studied by low-temperature photoluminescence and room-temperature stimulated emission measurements. Large strain-free ZnSe single crystals with a diameter as large as 5 cm have been grown uniformly without twinning by the SPVT technique. A variety of ZnSe samples, the as-grown and post-growth treated as well as intentionally doped crystals, were prepared in this study. Low-temperature photoluminescence measurements showed that near band edge I1d line and its LO phonon replicas dominated the spectra, and that donor-acceptor pair emission signatures were absent for SPVT as-grown samples; the intensity of the I1d, line decreased considerably and the I3 line became predominant after Zn extraction treatment. The pressure dependence on the bound exciton emission lines suggested that the I3 line might originate from excitons bound to a donor-like deep centre rather than to ionized shallow donors. The room-temperature optically pumped stimulated emission and blue lasing from the as-grown samples demonstrated that SPVT ZnSe single crystals have the quality sufficient to develop low-threshold, high-power output blue lasers.