Photoluminescence emission in deep ultraviolet region from GaN/AlN asymmetric-coupled quantum wells

We have investigated the photoluminescence spectra from GaN/AlN asymmetric-coupled quantum wells grown by metal-organic chemical vapor deposition. Deep ultraviolet photoluminescence peaks with photon energies up to 5.061 eV and dramatically improved intensities at low temperatures are identified due to recombination of electrons in the AlN coupling barrier with heavy holes in the GaN quantum wells. Photoluminescence quenching caused by relocation of photogenerated electrons under large internal electric fields, inherent in GaN/AlN asymmetric-coupled quantum wells, is observed.