Arrangement of nitrogen atoms in GaAsN alloys determined by scanning tunneling microscopy

The pair distribution function of nitrogen atoms in GaAs0.983N0.017 has been determined by scanning tunneling microscopy. Nitrogen atoms in the first and third planes relative to the cleaved (110) surface are imaged. A modest enhancement in the number of nearest-neighbor pairs particularly with [001] orientation is found, although at larger separations the distribution of N pair separations is found to be random. </em

In-situ ellipsometry: Identification of surface terminations during GaN growth

Spectroscopic ellipsometry (SE) is used to determine GaN surface termination during growth with metal-organic vapor phase epitaxy (MOVPE) by a correlation to well known results of plasma-assisted molecular beam epitaxy (PAMBE). The results manifest that in MOVPE under typical growth conditions the surface is not terminated by a Ga-bilayer as suggested for MBE. Moreover, it turns out that ellipsometry can be used to characterize the surface reconstruction in wurtzite GaN similar as reflectance anisotropy does for cubic III–V-compounds. The optical spectra for the PAMBE reveal clear differences between growth under Ga-rich and N-rich conditions, which are attributed to the presence of a Ga-bilayer and various N-rich reconstructions on the surface [1]. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</p

Distribution of nitrogen atoms in dilute GaAsN and InGaAsN alloys studied by scanning tunneling microscopy

Nitrogen atoms in the cleaved (1 -1 0) surfaces of dilute GaAsN and InGaAsN alloys have been studied using cross-sectional scanning tunneling microscopy. The distribution of nitrogen atoms in GaAs0.983N0.017 and In0.04Ga0.96As0.99N0.01 alloys is found to be in agreement with random statistics, with the exception of a small enhancement in the number of [001]-oriented nearest neighbor pairs. The effects of annealing on In0.04Ga0.96As0.99N0.01 alloys has been studied by scanning tunneling spectroscopy. Spectra display a reduced band gap compared to GaAs but little difference is seen between as-grown versus annealed InGaAsN samples. In addition, voltage dependent imaging has been used to investigate second-plane nitrogen atoms.</p

Surface termination during GaN growth by metalorganic vapor phase epitaxy determined by ellipsometry

Spectroscopic ellipsometry is used to study GaN films during growth by metalorganic vapor phase epitaxy (MOVPE) in correlation to well known results of plasma-assisted molecular beam epitaxy (PAMBE). Results for the PAMBE reveal clear differences between growth under Ga-rich and N-rich conditions, which are attributed to the presence of a Ga bilayer on the surface (also seen with low energy electron diffraction) in the Ga-rich case. Results for MOVPE surfaces during growth or for surfaces which are stabilized under NH3 are very similar to the N-rich PAMBE result. It is concluded that under normal growth conditions in MOVPE in contrast to PAMBE the surface is not terminated by a Ga bilayer. © 2003 American Institute of Physics.</em