Immiscibility behind the metalorganic vapor phase epitaxy of ingan

Abstract

The vapor-solid phase equilibrium and the solid composition versus input group-III ratio relationship for the metalorganic vapor phase epitaxy of InGaN are analyzed on the basis of standard thermodynamics. Immiscibility is inherent in the activities of the InN and GaN components. A miscibility gap (MG) definitely appears in the vapor-solid phase equilibrium below the critical temperature. At a given temperature, the equilibrium partial pressures are fixed at those for the binodal compositions across the MG. In the solid composition versus input group-III ratio diagram, the MG at a given temperature is represented by a straight line which gives a weighted average of the binodal compositions for a given input group-III ratio. The apparently uniform compositions observed in low-temperature growth may be attributed to the non-equilibrium "freeze-out" effect of the growth species due to the slow surface kinetics.