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ZnSe 1-x Te x and Be y Zn 1-y Se 1-x Te x bulk crystals were grown using the traveling solvent method (TSM) with tellurium solution. Ternary bulk crystals of ZnSe 1-x Te x contained tellurium from 1.2 to 3.6 at% (0.025 < x < 0.072). Quaternary bulk crystals of Be y Zn 1-y Se 1-x Te x contained tellurium from 1.8 to 7.8 at% and beryllium from 0.02 to 6.9 at% (0.03 < x

ZnSe single crystals were grown using the horizontal traveling solvent method (TSM) with selenium (Se) solution. The best FWHM of the X-ray rocking curve showed 26 arcsec and the lowest etch pit density was 1.4×10 5 /cm 2 . The ZnSe crystals exhibited an I 1d peak in a photoluminescence spectrum, implying little unintentional doping of impurities. The relationship between the ZnSe crystallinity and the dissolution time of ZnSe source implies a small diffusion coefficient for the liquid Se. The ZnSe molecule diffusion coefficient in liquid Se around 1060°C was estimated to be (3.3±0.6)× 10 −10 m 2 /s, derived from the dissolution time. The small diffusion coefficient may be due to the slow movement of ZnSe molecules in an associated solution.

We have performed for the first time a detailed transmission electron microscopic evaluation of CdTe layers grown on (0001) sapphire substrates by metalorganic chemical vapor deposition. From plan-view observation, it has been found that (111)-oriented CdTe grows on the (0001) sapphire substrates, and that a high density of dislocations and stacking faults are generated in the crystal. Typical dislocation densities are in the range 5 × 108 - 1 × 109cm−2. Several types of dislocations are found as follows: (i) threading dislocations; (ii) dislocation clusters; (iii) dislocation networks. Contrast experiments indicate that most of the dislocations have Burgers vectors of 12a inclined or parallel to the (111) plane. Stacking faults are generated both from the hetero-interface and within the epilayer. The former lie on two of the three equivalent {111} planes, whereas the latter is tetrahedral-shaped, consisting of three stacking faults of vacancy type on the three equivalent {111} planes. The total stacking fault density was estimated to be ≈ 106cm−2. From electron diffraction analysis of cross-sectional specimens, it has been found that the [1120] direction in the sapphire corresponds to the [110] direction in the CdTe layer. In the diffraction patterns, twin-related extra spots are found. Dark-field images taken from one of these spots reveals lamellar twins in the CdTe layer. They often terminate on planes nearly normal to the growth surface. They are generated throughout the epilayer, and their thickness is in the range 5–60 nm. In high resolution electron images, these lamella twins are also observed at an atomic scale. The defect structures described above are very similar to those observed in CdTe on (111)B GaAs.

We studied model lattice matching in the growth direction by tilt growth and found that the ratio of the tilt angle of the epilayer (α) to the offset angle of the substrate (θ) had a maximum at α / θ = 0.73, independent of the offset angle. Experimental plots of the ratio versus the full width at half maximum (FWHM) of (333) CdTe rocking curves in double-crystal X-ray diffraction show that the ratio ranges from 0.05 to 0.6 while the FWHM varies from 1100 to 400 arc sec. This result suggests that the lattice inclination orients the lattice structure perpendicular to the CdTe-sapphire heterointerface and that the tilt angle reduces defects such as dislocations and stacking faults. Most epilayers grown on sapphire substrates with offset angles above 3° were confirmed to have a α / θ ratio below 0.2. This suggests that crystal defects may be generated by shearing stress due to large offset angles. Greater defect density lowers the ratio and degrades crystallinity.