Analysis of InAs(001) surfaces by reflectance anisotropy spectroscopy - art. no. 193301

Reflectance anisotropy spectroscopy (RAS) was applied to study the reconstr ucted surfaces of InAs(001) at room temperature. Arsenic-capped InAs sample s, grown by molecular beam epitaxy, were annealed in ultrahigh vacuum. Low energy electron diffraction shows that, following As decapping, a 2 x 4 pha se (As-rich) is obtained after annealing the sample at 340 degreesC (10 min s), while a subsequent annealing at 450 degreesC (15 mins) yields a 4 x 2 p hase (In-rich). Using Kramers-Kronig relations, the anisotropy of the imagi nary part of the surface dielectric function (Delta epsilon (s)") between [ (1) over bar 10] and [110] directions of the substrate has been obtained fr om RAS data. We present both the RAS and Delta epsilon (s)" spectra charact eristic of (2x4) and (4x2) reconstructed InAs(001) surfaces, and interpret the appearing features in terms of surface-state transitions and bulk trans itions (modified by the surface). The experimental data are compared with t he case of GaAs(001). Below 3 eV, the presence of As and In dimers at the s urface gives rise to optical anisotropies centered at 2.4 and 1.7 eV, respe ctively, with opposite polarizations depending on the dimer-bond direction. At higher energies, a structure related to E-o' bulk critical point (at 4. 4 eV) is visible.