We have investigated intersubband absorption of GaN/Al0.58Ga0.42N multiple quantum well structures of high quality, which were grown by tow-pressure metal organic chemical vapor deposition (MOCVD). The crystalline quality and uniformity of the AlGaN barriers were improved by suppressing gas-phase parasitic reaction between NH3 and TMAl. This, in turn, produced a very sharp intersubband absorption spectrum with a spectral linewidth as narrow as 35 meV. (C) 2002 Elsevier Science B.V. All rights reserved.