Dominant transverse-electric polarized emission from 298 nm MBE-grown AlN-delta-GaN quantum well ultraviolet light-emitting diodes

摘要: III-nitride based ultraviolet (UV) light emitting diodes (LEDs) are of considerable interest in replacing gas lasers and mercury lamps for numerous applications. Specifically, AlGaN quantum well (QW) LEDs have been developed extensively but the external efficiencies which remain less than 10% wavelengths <300 nm due to high dislocation density, difficult p-type doping most importantly, physics band structure from three degeneration valence subbands. One solution address this issue at deep UV is by use AlGaN-delta-GaN QW where insertion delta-GaN layer can ensure dominant conduction (C) - heavyhole (HH) transition, leading large transverse-electric (TE) optical output. Here, we proposed investigated polarization-dependent characterizations AlN-delta- GaN LED ~300 nm. The grown Molecular Beam Epitaxy (MBE) ~3-4 monolayer (QW-like) sandwiched 2.5-nm AlN sub-QW layers. analysis shows that AlN-delta-GaN ensures a larger separation between top HH subband lower-energy bands, strongly localizes electron wave functions toward center hence resulting ~30-time enhancement TEpolarized spontaneous emission rate, compared conventional Al0.35Ga0.65N QW. electroluminescence measurements confirm our theoretical analysis; TE-polarized was obtained 298 with minimum transverse-magnetic (TM) polarized emission, indicating feasibility high-efficiency emitters on structure.