MBE growth of sharp interfaces in dilute-nitride quantum wells with improved nitrogen-plasma design

Analysis of structural and luminescence properties of GaAsN epilayers grown by molecular beam epitaxy (MBE) and chemical beam epitaxy on GaAs (001) substrates indicates the possibility of fabricating high nitrogen content (x > 0.03) alloys. The conventional plasma source design where nitrogen flux is controlled using a manual shutter was first implemented. Investigation of structural and optical properties by photoluminescence, high-resolution x-ray diffraction, secondary-ion mass spectrometry, and electron microscopy indicated the presence of thin parasitic layers formed during nitrogen plasma ignition, as well as significant N contamination of GaAs barrier layers, which could severely affect carrier extraction and transport properties in targeted devices. In order to overcome these limitations, a gate-valve-activated run-vent design was implemented that allowed the plasma to operate continuously during MBE growth, while N plasma flux changes during growth were monitored. The potential of this design for achieving very sharp switching schemes compatible with the fabrication of complex dilute-nitride quantum well structures, while preventing N contamination of GaAs barriers, was demonstrated.