GaN epitaxial layers at low-doping concentrations around 1 X 10(16)cm(-3) for power devices have been grown on low-dislocation-density GaN substrates. The epitaxial layers have shown much less-compensated behavior in net doping concentration, which arises from their much high-purity nature than those on sapphire substrates. Schottky barrier diode fabricated on the layer have shown extremely low leakage current and high breakdown voltage of 580 V, and low specific on-resistance of 1.3 m Omega cm(2), as expected from its high-quality epitaxial layer. (c) 2006 Elsevier B.V. All rights reserved.