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 fi lms of A3B5 semiconductors covers a broad range of phenomena in solid state physics and semiconductor technology, specifi ed by the processes of selforganization 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 GaxIn1-xP alloys with atomic ordering grown by MOCVD in a coherent way on GaAs (100) substrates. Epitaxial layers of GaxIn1–xP with ordering matched by the parameter of the crystal lattice with singlecrystalline 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 refi ned 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 GaxIn1-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 GaxIn1–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 fi rst time, the crystal lattice parameter was calculated for GaxIn1-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).

Keywords

• GaxIn1–xP
• atomic ordering
• epitaxial solid solutions.