The 415 nm laser diode structures of (AlGaIn)N were grown using metalorganic chemical vapor-phase epitaxy on bulk GaN substrates obtained using a high-pressure, high-temperature method. These substrates have the lowest dislocation density so far reported of less than 100 cm(-2). Defect-selective etching performed on a laser diode structure using molten bases at a temperature of 450 degrees C revealed dislocations at a density of 105 cm(-2). As the etching rate is different for every part of the epistructure, it was possible to determine the depth at which the dislocation was created. We found that about 25% of dislocations originated at the lower cladding layer of AlGaN, 60% at the quantum wells and 15% at the electron-blocking layer. (c) 2006 Elsevier B.V. All rights reserved.