Unstable mixing region in wurtzite In1-X-YGaXAlYN

In In1-xGaxN epitaxially grown by MOVPE, phase separation is experimentally found to occur at an indium composition of more than 20% from X-ray diffraction and microscopic examination using an analytical electron transmission microscope. Fitting the spinodal isotherms calculated from the free energy of mixing based on a strictly regular solution approximation using delta-lattice-parameter method to the experimental data, the constant of proportionality K between a lattice constant and the pseudobinary interaction parameter is determined. Using this K value, the pseudobinary interaction parameter is calculated using the delta-lattice-parameter method, and the unstable mixing region in a wurtzite structure In1-X-YGaXAlYN quaternary system is predicted. (C) 1998 Elsevier Science B.V. All rights reserved.