Whisker structures and quantum dots fabricated by photoelectrochemical (PEC) etching of undoped and doped metalorganic chemical vapor deposition (MOCVD)-grown GaN (2 x 10(17) or 3 x 10(18) cm(-3)) are investigated in relation with their field-emission characteristics. Different surface morphologies, corresponding to different etching time and photocurrent, results in different field-emission characteristics with low turn-on voltage down to 4 V/mum and the appearance of quantum-size effect in the I-V curves. (C) 2003 Elsevier B.V. All rights reserved.