Iodine-assisted molecular beam epitaxy

Abstract

Iodine was introduced into our solid source molecular beam epitaxy chamber during the growth of GaAs and AlGaAs layers and strained-layer InGaAs quantum wells. Photoluminescence spectra of these samples taken at 4.2 K were compared to spectra from a series of test samples which were grown in the absence of iodine flux. We have observed a general improvement of the material quality of AlGaAs layers grown at substrate temperatures around and below 600°C since the introduction of iodine into our chamber regardless of whether an iodine flux impinged on the substrate during the growth process or not. Strong excitonic peaks with full width at half maximum of only 8 meV were observed in 4.2 K photoluminescence spectra of undoped Al 0.2 Ga 0.8 As layers grown at substrate temperatures as low as 550°C using As 4 . The epitaxial layers grown since the introduction of iodine are the brightest Al 0.2 Ga 0.8 As samples that we have obtained from our molecular beam epitaxy system. These results suggest that the presence of iodine in a molecular beam epitaxy system can result in improved optical properties for AlGaAs. The 4.2 K photoluminescence spectra and secondary ion mass spectroscopy depth profiles also show that iodine preferentially removes Ga from AlGaAs layers during growth, resulting in layers with higher Al content.