Aligned carbon-hydrogen complexes in GaAs formed by the decomposition of trimethylgallium during low-pressure metal-organic vapor-phase epitaxy.

Abstract

Highly carbon-doped (001)-oriented GaAs layers have been grown by low-pressure metal-organic vapor-phase epitaxy using the precursor trimethylgallium (TMG) to obain [C] in excess of 1\ifmmode\times\else\texttimes\fi{}${10}^{20}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$. Post-growth infrared measurements using polarized light demonstrate that grown-in planar carbon-hydrogen [H-(${\mathrm{C}}_{\mathrm{As}}$${)}_{2}$] complexes, giving vibrational absorption at 2688 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, have the two ${\mathrm{C}}_{\mathrm{As}}$ atoms aligned along the [1\ifmmode\bar\else\textasciimacron\fi{}10] direction. This orientation is orthogonal to that found previously for samples grown by metal-organic molecular-beam epitaxy on a (001) GaAs (2\ifmmode\times\else\texttimes\fi{}4) reconstructed surface. The formation of the complex is attributed to incomplete decomposition of the TMG and models are proposed to explain the difference in the orientation for the two growth methods.