Quasiparticle dynamics of an optimally doped Bi2Sr2CaCu2O8+δ single crystal is investigated by the femtosecond pump-probe technique. Temperature dependences of amplitude of the photoinduced differential reflectivity and the relaxation time show the evidence of strong phonon bottleneck. The experimental results are analysed by the Rothwarf–Taylor model.

Temperature-dependent absorption spectra in temperature range of 11—300K are recorded for a series of unintentionally doped HgCdTe grown by liquid phase epitaxy. The abnormal energy shift of about 7—20meV of absorption edge in the low temperature range (<70K) has been analyzed. The results suggest this the phenomenon to be caused by the Hg vacancies and the abnormal red-shift is related to the composition and the carrier density of the materials. The Hg vacancy level is estimated to be at 20meV above the valence band, which is well consistent with the results of Hg vacancy acceptor level calculated by the empirical expression. The results may provide a preliminary explanation that the bandgap obtained by the conventional transmission spectroscopy is slightly higher than the cutoff energy of the photocurrent response in practical device applications.

Based on the relationships between stress and strain in an arbitrary coordinate system, the elastic theory of crystal and the dislocation gliding theory, the critical thicknesses of HgCdTe/CdZnTe oriented in the ［111］ and ［211］ directions are calculated, and the dependence of the critical thickness of HgCdTe on substrate composition and film composition are studied. The results show that the critical thickness of HgCdTe depends sensitively on substrate composition and film composition. For 10μm films oriented in the ［111］ direction prepared by liquid phase epitaxy, the substrate composition and the films composition must match to within ±0.225‰ and ±5‰, respectively, to prevent the occurence of misfit dislocations. In addition, for 10μm films oriented in the ［211］ direction prepared by molecular beam epitaxy, the actual ranges of zinc composition and the films composition are ±0.2‰ and ±4‰ for the films to remain below the critical thickness, respectively.

High_resolution x_ray diffraction technology is applied to the measurement of la ttice parameters and the study of strain for Hg1-xCdxTe fi lms gr own by molecular beam epitaxy. The results show that there exist both perpendicu lar strain and shear strain in Hg1-xCdxTe films. Based on crystal elastic theory, strain states in Hg1-xCdxTe films are analyz ed and calculated, and the lattice parameters of 1-xCdxTe film s at the relaxation state are obtained. It is found that the relationship betwee n lattice parameters and compositions of Hg1-xCdxTe films agrees with Vegard's law, rather than Higgins formula proposed in earlier research. It is also found that the lattice parameters can be derived from the measured data of (224) plane spacing, and that the compositions of Hg1-xCdxTe films can also be evaluated by using Vegard's law with an error about 0 01.