Evidence of oxygen in undoped InAlAs MOVPE layers

InAlAs layers lattice matched to InP were grown by LP-MOVPE (low-pressure metal-organic vapor-phase epitaxy). The layers were characterized with respect to deep levels by C-V, SIMS (secondary ion mass spectroscopy) and photocapacitance measurements. Oxygen was definitely found by SIMS measurements and temperature-dependent C-V measurements as the most important defect impurity stemming from the epitaxial sources. The activation energy was determined to Delta E/sub T/=85 meV. The concentration strongly depends on the growth condition. High growth temperatures lead to low concentrations of oxygen and silicon. The lower limit is given by the quality of the precursors, the gas purifying system, and the growth conditions. Four deeper levels have been found with low concentrations with no significant influence on the layer properties.<>