GaN nanowire surface state observed using deep level optical spectroscopy

Deep level defects in n-type GaN nanowires (NWs) with and without an epitaxially-grown AlGaN shell were compared using photoconductivity-mode deep level optical spectroscopy. Hole photoemission from a defect state located approximately 2.6 eV above the valence band was observed for GaN NWs but was not observed for AlGaN/GaN core-shell NWs, indicating that this deep level is associated with a GaN surface state. Identifying GaN NW surface states and developing an effective passivation mechanism is expected to aid in the understanding and improvement of GaN NW-based sensors and optoelectronics.