ATOMIC ORDERING IN SOLID SOLUTIONS GaxIn1–xP: EXPERIMENTAL STUDY OF THE STRUCTURAL AND MORPHOLOGICAL PROPERTIES

Abstract

Alloys based on A₃B₅ semiconductors have attracted the interest of researchers of semiconductor optoelectronics. These alloys are characterized by a positive formation enthalpy that facilitates superstructure ordered phases on the basis of these alloys, with formation of a domain structure under certain technological conditions. The spontaneous appearance of periodically ordered structures on the surface and in the epitaxial films of A₃B₅ semiconductors covers a broad range of phenomena in solid state physics and semiconductor technology, specified by the processes of self-organization in the condensed matter. This is of particular interest for the production of semiconductor nanostructures with typical sizes of ≤ 100 nm. This phenomena of the ordering appearance in A₃B₅ allows the inclusion of narrow-band semiconductors in a wide-band gap matrix and vice versa, thus creating a localizing potential for the current carriers. Periodical structures of these inclusions can form superlattices comprised of quantum wells, wires or quantum dots. Furthermore, the spontaneous appearance of the nanostructures provides a basis for a new technology for the production of ordered arrays of irregularities, moreover, the basis for the next generation opto- and microelectronics.

The aim of this study was to investigate the structural properties of epitaxial Ga_xIn_1-xP alloys with atomic ordering grown by MOCVD in a coherent way on GaAs (100) substrates.

Epitaxial layers of Ga_xIn_1-xP with ordering matched by the parameter of the crystal lattice with single-crystalline GaAs (100) substrates were grown by MOCVD in a horizontal reactor. The structural quality of the heterostructures and determination of the lattice parameters in the alloys were performed by X-ray diffraction with an X-ray diffractometer DRON 4-07 and characteristic radiation of cobalt. The study of the surface morphology was performed by atomic-force microscopy using a NTEGRA Therma (NT MDT) microscope. The concentration of the elements in the alloys was refined by X-ray microanalysis using an Oxford Instruments attachment to the electron microscope JEOL.

Using a set of structural and microscopic methods, the properties of epitaxial Ga_xIn_1-xP alloys with the ordered arrangement of the atoms in a crystal lattice grown by MOCVD on single-crystalline GaAs (100) substrates were studied. It was shown that in the conditions of coherent growth of Ga_xIn_1-xP alloy on the GaAs (100) substrate, the observed atomic ordering and tetragonal distortion resulted in the change in the crystal lattice parameter. Consequently, this led to a reduction in the crystal symmetry, formation of two different nanorelief types on  the surface in comparison with the properties of disordered alloys. For the first time, the crystal lattice parameter was calculated for Ga_xIn_1-xP alloys with ordering grown in a range of compositions corresponding to coherent growth taking into account the elastic stresses on GaAs (100) substrates dependent on the order parameter (long-range ordering).

ACKNOWLEDGMENTS

The work in the part of creating epitaxial heterostructures with high functional properties was carried out with the support of the grant of the President of the Russian Federation MD-188.2017.2 and MK-4865.2016.2.

The work, in the part of managing the morphology, the composition of the surface, and the functional characteristics of low-dimensional systems, was carried out with the financial support of the RFBR grant 16-32-00020 mol_a.

The results of the research were obtained using the equipment of VSU's Equipment Centre for Collective Use of Scientific Equipment