Arsenic adsorption and exchange with phosphorus on indium phosphide (001)

Arsenic adsorption and exchange with phosphorus on indium phosphide (001) have been studied by scanning tunneling microscopy, low-energy electron diffraction, and x-ray photoelectron spectroscopy. The surface phase diagram as a function of temperature has been obtained. At 285 degreesC, arsenic adsorbs on the InP sigma(2x4) surface (P coverage=0.25 ML), forming a disordered (1x4) with double layers of arsenic (As+P coverage similar to1.5 ML). At 330 degreesC, arsenic adsorbs on the sigma(2x4), producing a (2x1) structure with a complete monolayer of group-V dimers. By contrast, some phosphorus desorption occurs above 350 degreesC, allowing arsenic to displace the phosphorus in the top few layers and converting the sigma(2x4) to the beta2 and alpha2(2x4) reconstructions (As coverage 0.75 and 0.50 ML, respectively). Above 430 degreesC, arsenic exchange with InP yields an InAs (4x2) reconstruction. Quantitative analysis of the x-ray photoemission spectra has revealed that substitution of arsenic for phosphorus is limited to the top two to three surface bilayers.