Magnetophotoluminescence characterization of residual donors in GaAs grown by metalorganic chemical vapor deposition

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Abstract
The residual donor species in undoped GaAs epilayers grown by metalorganic chemical vapor deposition have been characterized by magnetophotoluminescence (MPL) measurements at high magnetic fields (7 T). Most samples were grown using trimethylgallium and arsine, but samples grown using the liquid group-V source t-butylarsine were also studied. The results show good agreement with identifications previously made in high-purity samples (NA+ND≤5×1014 cm−3) at zero magnetic field, but with greatly improved spectral resolution and signal levels. With the MPL technique, residual donor species were resolved even in relatively impure samples (NA+ND=1×1016) for which no information was obtained at zero magnetic field. For the samples grown with arsine, Ge donors were observed to predominate in the high-purity samples, but Si was the dominant donor in the lower-purity samples. The Si impurity was traced to contamination from a quartz baffle in the growth chamber. Lower levels of sulfur donors were observed in many samples. Sulfur was found to be the second most predominant donor after Ge in samples grown with t-butylarsine.