Electron confinement in strongly coupled GaN/AlN quantum wells

The electron confinement in double GaN/AlN quantum wells coupled by an ultrathin AlN barrier has been investigated by means of structural and optical measurements. The intersubband absorption spectra present two peaks attributed to the e(1)-e(2) and e(1)-e(3) transitions, respectively. The results of photoluminescence and intersubband spectroscopies are compared with simulations of the electronic structure based on the envelope function formalism. A good agreement is obtained for all investigated samples. These results provide clear evidence that the potential drop at the GaN/AlN heterointerfaces is not abrupt, but is spread over one monolayer.