Strain Accommodation in GaSb/AlSb Superlattices on (001) GaSb Substrates with AlSb Buffers

We report the observation that AlSb layers thinner than the epilayer critical thickness for the onset of plastic relaxation undergo lattice relaxation when used as buffers for GaSb/AlSb superlattices on (001) GaSb substrates. It is found that this is induced by the external stress from the overlaying superlattice, and that the mechanism is consistent with relaxation processes involving the nucleation and expansion of half-loops earlier suggested for strained epilayers. Photoluminescence spectroscopy conforms with the in-plane strains calculated from double-crystal and small-angle X-ray diffraction measurements.

Source:IOPscience

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Multiple-scattering effects in Ga K-edge extended x-ray absorption fine structure spectra of GaP, GaAs and GaSb semiconductor compounds

The dependence of Ga K-edge multiple-scattering extended x-ray absorption fine structure (MS-EXAFS) effects on the nearest neighbours in GaP, GaAs and GaSb semiconductor compounds with the zinc blende structure has been comprehensively investigated by considering the coordination environment within the first three shells around the Ga atoms. It is revealed that in the case of GaP with a light element as the first neighbour of the Ga absorber, the MS-EXAFS effects are negligibly weak with respect to the single-scattering (SS) contribution. For GaAs and GaSb compounds with heavier elements as the first neighbour of the Ga absorber, the MS effects become increasingly important and are dominated by a triangular double-scattering path DS2 (\mathrm {Ga}_{0} \to \mathrm {B}_{1} \to \mathrm {B}_{2} \to \mathrm {Ga}_{0} ). The EXAFS contribution of the DS2 path destructively interferes with that of the second shell single-scattering path (SS2), with the amplitude ratio of DS2 to SS2 rising from 7% for GaP to 25 and 70% for GaAs and GaSb, respectively. This indicates that the second shell peak magnitude for these compounds is increasingly damped by the MS effects as the first nearest neighbour goes from P to Sb. Based on these results, we present a generalized and simplified high-shell MS-EXAFS analysis method for compounds with the open structure of zinc blende.

Source:IOPscience

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High-crystalline GaSb epitaxial films grown on GaAs(001) substrates by low-pressure metal–organic chemical vapor deposition

Orthogonal experiments of GaSb films growth on GaAs(001) substrates have been designed and performed by using a low-pressure metal–organic chemical vapor deposition (LP-MOCVD) system. The crystallinities and microstructures of the produced films were comparatively analyzed to achieve the optimum growth parameters. It was demonstrated that the optimized GaSb thin film has a narrow full width at half maximum (358 arc sec) of the (004) ω-rocking curve, and a smooth surface with a low root-mean-square roughness of about 6 nm, which is typical in the case of the heteroepitaxial single-crystal films. In addition, we studied the effects of layer thickness of GaSb thin film on the density of dislocations by Raman spectra. It is believed that our research can provide valuable information for the fabrication of high-crystalline GaSb films and can promote the integration probability of mid-infrared devices fabricated on mainstream performance electronic devices.

Source:IOPscience

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