Low current laser operation at 405 nm has been demonstrated for the first time for the devices fabricated on sapphire substrates by metalorganic chemical vapor deposition (MOCVD) using a high-temperature-grown single-crystal AIN buffer. The thick optical guiding layers were adopted to improve optical confinement. The device structure was the 2-mu m-wide ridge-stripe type without facet coating. The minimum threshold current and current density were 60 mA and 3.8 kA/cm(2) for cavity lengths of 500 mm and 1 mm, respectively. These data were comparable to those reported using the special dislocation reduction techniques. The threshold current density linearly decreases with decreasing inverse of cavity length. It was expected that the low threshold current density ranging from I to 2 kA/cm(2) could be realized by adapting high reflection coating for laser facets. This expected current density was comparable to values realized for devices grown on the thick freestanding GaN as substrates. These findings support the promising potential of the HT-AlN buffer technique for production of advanced short-wavelength light-emitting devices on sapphire substrates. (c) 2006 Elsevier B.V. All rights reserved.