High-performance 370 nm ultraviolet light-emitting diodes (UV-LED) with an AlGaN/InGaN single quantum well structure were fabricated on sapphire substrate by using the metal organic chemical vapor deposition (MOCVD) technique. Three group different growth conditions of undoped n-side barrier and p-side barrier were chosen to sandwich the InGaN well layer in the LED samples. By using high-Al content and symmetric composition n- and p-side barriers, the output efficiency of our UV-LED has been greatly improved. An output power of 2.5 mW at an injection current of 20mA was achieved. (C) 2003 Elsevier B.V. All rights reserved.