Methods and systems produce flattening layers associated with nitrogen-containing quantum wells and prevent 3-D growth of nitrogen containing layers using high As fluxes. MEE (Migration Enhanced Epitaxy) is used to flatten layers and enhance smoothness of quantum well interfaces and to achieve narrowing of the spectrum of light emitted from nitrogen containing quantum wells. MEE is performed by alternately depositing single atomic layers of group III and V before, and/or after, and/or in-between quantum wells. Where GaAs is used, the process can be accomplished by alternately opening and closing Ga and As shutters in an MBE system, while preventing both from being open at the same time. Where nitrogen is used, the system incorporates a mechanical means of preventing nitrogen from entering the MBE processing chamber, such as a gate valve.