Strain relaxation has been studied for the 10‐period quantum well (QW) heterostructures grown by MOVPE, In0.16Ga0.84N/GaN and In0.2Ga0.8N/GaN, both emitting with high efficiency in the blue and green regions, respectively. Additionally, a set of high‐In content InGaN/GaN QW structures, where growth parameters were kept constant but QW numbers varied between 1 and 10, were also analysed by TEM, XRD and PL. For the highly‐efficient green and the set of variable QW samples, TEM structural studies identified large well‐width fluctuations and misfit dislocations that thread into the sample surface and are generated in the quantum well stack. This contrasts with similar observations of blue‐emitting MQWs where misfit dislocations are not seen. PL measurements have been carried out for the In‐rich QW series and did not reveal a greater degradation of the optical properties with increasing numbers of quantum wells in the stack. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Stimulated emission at 374.9 nm has been observed in an optically pumped Cd,,zzZnO,,sS-ZnS strained-layer superlattice at room temperature. Using a pump-and-probe technique with nanosecond excitation pulses, optical gain has also been observed at the tail part of the n= 1 heavy-hole exciton absorption spectrum in the presence of the clear absorption peak of the exciton. Our experimental results suggest that the stimulated emission originates from excitonic gain.

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This paper reports on a detailed study of the development of the close space sublimation method, which has been widely used in the preparation of polycrystalline CdTe/CdS solar cells, as an epitaxial method for the growth of thick CdTe single crystal films over 200 lm on GaAs and Ge substrates for highenergy radiation detectors. The resulting microscopic growth phenomena in the process are also discussed in this paper. High-quality single crystalline CdTe thick films were prepared with x-ray rocking curves full width at half maximum (FWHM) values, which were $100 arcsec on Ge substrates and 300 arcsec on GaAs substrates. The quality of thick films on Ge(100) showed a substantial improvement with nucleation in a Te-rich growth environment. No Te inclusions in the CdTe films grown on GaAs(211)B and Ge(100) were observed with IR transmission imaging. Photoluminescence of CdTe/Ge shows a large reduction in the 1.44 eV defect energy bands compared with films grown on GaAs substrates. The film resistivity is on the order of 10 10 X cm, and the film displayed some sensitivity to alpha particles.