Epitaxial layers of GaAs have been grown by metalorganic molecular beam epitaxy (MOMBE) with atomic carbon concentrations ranging from 4 X 10 17 to 3.5 X Ufo cm-I. The dependences of GaAs lattice parameter and hole concentration on atomic carbon concentration have been determined from x-ray diffraction, Hal! effect, and secondary-ion mass spectrometry measurements. For atomic carbon concentrations in excess of 1 X Wi'! cm-3, the hole concentrations are less than the corresponding atomic carbon concentrations. Lattice parameter shifts as large as 0.2% are observed for carbon concentrations in excess of 1 X 10 20 em-3, which results in misfit dislocation generation in some cases due to the lattice mismatch between the C-doped epllayer and undoped substrate. Over the entire range of carbon concentrations investigated, Vegard's law accurately predicts the observed lattice contraction.
High crystalline quality epitaxial CdTe(112)B/ZnTe films were deposited by molecular-beam epitaxy directly onto vicinal Si(112) substrates, without use of GaAs interfacial layers. The films were characterized with x-ray diffraction, optical microscopy, and wet chemical defect etching. Single crystal, twin-free CdTe(112)B films exhibit structural quality exceeding that previously reported for CdTe(112)B heteroepitaxy on GaAs/Si(112) or GaAs(112)B substrates. X-ray rocking curve full width at half-maximum of 72 arcsec for CdTe(224) reflection and near-surface etch pit densities (EPD) of 2×106 cm−2 have been observed for 8-μm-thick CdTe films. EPD depth profiles indicate that the threading dislocation density decreases with increasing II–VI epilayer thickness up to approximately 5 μm thickness and saturates at 2×106 cm−2 for thickness exceeding 5 μm. The CdTe epilayer orientation was observed to tilt 2° away from the Si(112) substrate orientation toward the [001] direction.
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