The sharp photoluminescence (PL) and optical-reflection spectra in the bandedge region of the high-quality nondoped ZnTe substrate (100) were observed at 4.2 K. Free exciton, associated with lower and upper polaritons (EX L and EX U ) at 2.382 eV and 2.381 eV, respectively, were clearly observed. This meant that this substrate was high quality. The intensity of a bound exciton peak (2.375 eV), which is caused by a Zn vacancy, of a neutral acceptor decreased with an increase of the Zn vapor pressures.

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Atomically flat, fully strained Si1−xGex layers with thicknesses ranging from 8 to 180 nm were grown on Si(001) at 450 °C by gas-source molecular beam epitaxy from Ge2H6/Si2H6 mixtures. We show that smooth, relaxed alloy layers are obtained, without the necessity of using several-microns-thick compositionally graded layers, via in situ rapid thermal annealing of fully strained Si1−xGex(001) layers at 1000 °C for 10 s. Relaxed Si0.75Ge0.25(001) layers with thicknesses of 100–180 nm were found to have surface widths of ≃5 nm, comparable to the best results obtained using thick graded buffer layers.

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