Ammonia nitridation of indium and gallium oxide precursors obtained through a soft solution route led to their oxynitrides [In-0.97 square(0.03)][N0.92O0.08] at 660 degrees C and [Ga-0.89 square(0.11)][N0.66O0.34] at 850 degrees C, respectively, where E] refers to a In or Ga vacancy. Cation vacancies in their wurtzite-type lattice were eliminated in similar preparations with the co-presence of Zn2+ by forming complete solid solutions of (InN)(1-x)(ZnO)(x) and (GaN)(1-y)(ZnO)(y). The optical absorption edge shape was found to be relatively steep at the solid Solution limits of x approximate to 0.23 and y approximate to 0.33 compared to the case without zinc. (C) 2009 Elsevier Ltd. All rights reserved.