Abstract:
We have examined multiple quantum well AIGaN/GaN structures with several quantum wells of
varying widths. The structures had strain-free quantum wells and strained barriers. Strong
piezoelectric fields in these structures led to a large red shift of the PL emission energies and long
decay times were also observed. While the peak energies could be modelled using the effective mass
approximation, the calculated free exciton radiative lifetimes were much shorter than those observed
in experiments, indicating an alternative recombination mechanism, tentatively attributed to localised
excitons. Cathodoluminescence depth profiling revealed an unusually small penetration range of
electrons suggesting that electron-hole pairs preferentially remain within the multiple quantum well
region due to the existing electric fields. Spatial fluctuations of the cathodoluminescence intensity
were also observed.
