Red shifts in photoluminescence (PL) peaks have been observed for Al{sub}0.25Ga{sub}0.75As grown by atomic hydrogen (H)-assisted molecular beam epitaxy (MBE) by an amount of as large as 80 meV compared to those grown without atomic H. Fromabsorption spectra measurements, the observed red shifts for with atomic H case were due to changes in the band-gap energies, and not due to changes in Al compositions nor formation of new H-related emission centers. It is thought that possible cause ofthe observed band-gap anomaly is related with spontaneous formation of an ordered superlattice during atomic H-assisted MBE.
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