Fabrication and optical studies of AlGaN/GaN quantum-well waveguides

We report the successful fabrication and optical study of submicron wavegui de structures based on AlGaN/GaN multiple-quantum wells (MQWs). The MQW str uctures were grown by metalorganic chemical vapor deposition on sapphire su bstrates and the waveguides were fabricated by electron-beam lithography an d inductively coupled plasma dry etching. The waveguides were patterned wit h a fixed width of 0.5 mum but with orientations varying from -30 degrees t o 60 degrees relative to the a axis of GaN. Optical emission from these str uctures was studied by photoluminescence spectroscopy. The peak position an d linewidth of the emission peak were found to vary systematically with the orientations of the waveguides and followed the sixfold symmetry of a wurt zite structure. This is most likely related to the anisotropy of the excito n/carrier diffusion coefficient along the different crystal orientations in the quasione-dimensional case. The implication from the results is that in proper designs of photonic and electronic devices where submicron structur es are fabricated in III nitrides one must consider the orientations of the structures. (C) 2001 American Institute of Physics.