BAlN thin layers for deep UV applications
Résumé
Boron containing III-nitrides are attractive system for deep-UV LEDs and LDs because of their wide bandgaps and flexible lattice. However the crystallinity and boron content have been limited due to large mismatch between BN and other nitrides. In this work, BAlN layers with boron composition from 1% to 5% were successfully grown on AlN template substrates by low-pressure organometallic vapor phase epitaxy. The samples were grown at 650˚C and then annealed at 1020˚C for recrystallization. Growth techniques such as temperature, growth time and TEB/III ratio in the gas phase were investigated. High quality BAlN layers were grown using flow-modulate epitaxy method that allows to enhance surface migration of boron atoms. 70 nm-thick layers show a good surface morphology. For the first time, clear XRD peak relating to 5% boron for this new material was observed, which suggests the formation of single-phase solid solution. Adding more boron to the AlN produced a shift in the peak positions to greater angles. Further results by TEM and optical characterizations will be presented. This new material is promising for deep-UV applications and gives more freedom for bandgap engineering of multi-structure devices.