Annealing in GaInNAs system

The effect of post-growth thermal annealing on crystallinity and bandgap in GaInNAs systems is systematically investigated. Annealing greatly improves the crystallinity of GaInNAs and also blue shifts the bandgap. This improved crystallinity is due to the elimination of non-radiative centres, and is not directly related to the blue shift in the bandgap. The blue shift may be closely related to the red shift in the bandgap seen when N is added to GaInNAs; if so, this would provide a clue to the reasons for the red shift in the bandgap of III–N–V alloys. The unexpected behaviour of the bandgap in GaInNAs is investigated by examining the bonds through optical phonons. We have found that the bandgap varies with the strength or length of the GaN bonds in GaInNAs. Annealing changes atomic positions in a unit cell of GaInNAs and thus blue shifts its bandgap.