Understanding the Anisotropy in the Electrical Conductivity of CuPt-type Ordered GaInP Thin Films by Combining TEM Biasing and First Principles Calculations.

In this work, the effect of CuPt ordering on the optoelectronic properties of GaInP is studied by combining transmission electron microscopy measurements and density functional theory (DFT) calculations. GaInP layers were grown by metal organic vapor phase epitaxy with a CuPt single-variant-induced ordering due to the intentional misorientation of the Ge(001) substrate. Moreover, the degree of order was controlled using Sb as the surfactant without changing other growth parameters. The presence of antiphase ordered domain boundaries (APDBs) between the ordered domains is studied as a function of the order parameter. The electrical measurements on a set of samples with controlled degree of order evidence a clear anisotropic electrical conductivity at the nanoscale between the [110] and [1-10] orientations, which is discussed in terms of the presence of APDBs as a function of the degree of order. Additionally, DFT calculations allow to determine the differences in the optoelectronic properties of the compound with and without ordering through the determination of the dielectric function. Finally, the anisotropy of the electrical conductivity for the ordered case is also discussed in terms of the effective mass calculated from the band structure on specific -paths. By comparing the experimental measurements and the theoretical calculations, two factors have been presented as the main contributors of the electric conductivity anisotropy of CuPt-type ordered GaInP thin films: antiphase boundaries that separate domains with uniform order (APDBs) and the anisotropy of the effective mass due to the alternating of In/Ga rich planes.