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 °C, arsenic adsorbs on the InP s(234) surface (P coverage50.25 ML), forming a disordered (134) with double layers of arsenic (As 1P coverage ;1.5 ML). At 330 °C, arsenic adsorbs on the s(234), producing a (231) structure with a complete monolayer of group-V dimers. By contrast, some phosphorus desorption occurs above 350 °C, allowing arsenic to displace the phosphorus in the top few layers and converting the s(234) to the b2 and a2(234) reconstructions ~As coverage 0.75 and 0.50 ML, respectively!. Above 430 °C, arsenic exchange with InP yields an InAs (432) 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.