Reflectance-difference spectroscopy of mixed arsenic-rich phases of gallium arsenide (001)

Abstract

The relationship between the reflectance difference spectra and the atomic structure of arsenic-rich reconstructions of GaAs͑001͒ has been investigated. Scanning tunneling micrographs reveal that a roughening process occurs as the surface structure changes with decreasing arsenic coverage from 1.75 to 0.75 monolayers ͑ML͒. At 1.65 ML As, small pits, one bilayer in depth and having the same c(4ϫ4) reconstruction as the top layer, form in the terraces. At the same time, gallium atoms are liberated to the surface, disrupting the c(4 ϫ4) ordering. At about 1.4 ML As, (2ϫ4) domains nucleate and grow on top of the c(4ϫ4). Further desorption of arsenic causes the underlying layer to gradually decompose into a metastable (2ϫn) phase (n ϭ2, 3, or 4͒, and finally into the (2ϫ4). In the reflectance difference spectra, negative peaks at 2.25 and 2.8 eV correlate with the c(4ϫ4)-type arsenic dimers. However, the intensity of the latter feature strongly depends on the presence of adsorbates, such as alkyl groups and gallium adatoms. By contrast, the intensity of the positive peak at 2.9 eV is directly proportional to the density of (2ϫ4)-type dimers.

Detection of surface states anisotropies at GaAs(001)(2 × 4) decapped surfaces

“…[28] and the shift of the zero-line observed during oxygen chemisorption. It has been already noted in literature that: (i) P1 and P3 coincide with bulk critical points E 1 and E 0 ′, respectively [15,[17][18][19]21]; (ii) the sign of P1 (positive, according to the assumed expression for RAS signal) is consistent with a higher reflectivity for light polarized along the direction of As-dimers at the surface; (iii) P1 is sensitive to contamination (oxygen [28], hydrogen [31], indium [32], germanium [33]), while P3 is weakly dependent upon surface conditions; (iv) the amplitude of P1 results proportional to the number of As-dimers present at the surface layer [34].…”

Ga–As dimer structure for the GaAs(001)-c(4×4) surface

“…In contrast, a well-ordered cð4 Â 4Þ arrangement was observed in STM images for the surfaces prepared using As 2 fluxes [2,3] and metal-organic vapor-phase epitaxy (MOVPE) [16], in which three As-As dimers structure is clearly identified. More interestingly, the shape of RD spectrum measured from the latter surface [16] is quite similar to those measured from the 5. Difference in formation energy per cð4 Â 4Þ unit cell between the Ga and As dimer and As and As dimer models as a function of Ga chemical potential.…”

Kinetics of tertiarybutylphosphine adsorption and phosphorus desorption from indium phosphide ()

“…After growth, the samples were transferred directly to the UHV system. A J-Y NISEL RDS spectrometer was used to obtain the spectra and transient data [18].…”