Semi-empirical modeling of the optical gap of amorphous hydrogenated nitrogenated carbon films

We report here results of modeling the optical gap of amorphous hydrogenated nitrogenated carbon films using semi-empirical methods. Parametric Method 3 (PM3) was used to optimize the geometry of oligomers. Using the PM3 geometrical data, Zerner's intermediate neglect of differential overlap calculations were carried out to simulate the absorption spectra of the films. We have analyzed the optical gap values as a function of the geometry and elemental composition of these materials. The theoretical results are contrasted with the experimental ones and used to estimate the actual conformations of the amorphous materials. The results indicate that this approach can be an efficient tool to analyze amorphous carbon films. (C) 2000 American Vacuum Society. [S0734-2101(00)08705-4].1852466247

Strong spatial beryllium doping selectivity on InGaP layers grown on pre-patterned GaAs substrates by chemical beam epitaxy

We present an investigation of beryllium doping selectivity in InGaP layers grown by chemical beam epitaxy on pre-patterned substrates. We observed a resistivity of 3.1 X 10(-2) and 4.5 x 10(-2) Omega cm for (1 1 1)A planes with the growth at 500degreesC and 540degreesC, respectively. The layers on (0 0 1) planes show a resistivity of 8.9 x 10(-1) Omega cm with the growth at 500degreesC, being essentially undoped with the growth at 540degreesC (.) We show how this strong doping selectivity can be explained by Be3P2 cluster formation growth, which depends on growth temperature and planar crystalline structure. (C) 2004 Elsevier B.V. All rights reserved.266442943