Anisotropic resistivity correlated with atomic ordering in <i>p</i>-type GaAsSb

Abstract

We have detected three- and six-fold lateral ordering in undoped and carbon-doped GaAs1−xSbx films (0.4&amp;lt;x&amp;lt;0.6), using plan-view and cross-sectional transmission electron microscopy. The samples were grown by organometallic vapor phase epitaxy onto oriented InP (001) substrates, at temperatures ranging from 500 to 600 °C. Spontaneous lateral superlattices with modulation parallel to the [110] in-plane direction occur with two periodicities, 6 or 3 times the random alloy 〈110〉 lattice parameter. The degree of ordering or domain size increases with growth temperature, as seen by increasing definition of the superlattice fringes in the images, and by a change from streaks to superlattice spots in the selected area diffraction patterns. While the formation mechanism is likely a surface mediated process, no differences were detected for samples in compression or tension, or between those undoped or carbon doped. The ordering correlates with large anisotropies of up to 150% in [110]/[11_0] sheet resistance ratios.