Abstract
Thermodynamic analyses were performed to understand the influence of lattice constraint from InN and GaN substrates on the relationship between input mole ratio R_<In> (=P_<In>^0/ (P_<In>^0 + P_<Ga>^0), where P^0_i is the input partial pressure of element i) and solid composition x in In_xGa_<1-x>N during molecular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE). For the both growth methods, the calculation results suggest that a compositionally unstable region is found at the InN-rich region for InGaN on GaN at higher temperatures while that for InGaN on InN can be seen at GaN-rich region due to the lattice constraint from the substrate. In case of the MOVPE, it is found that growth region of InGaN in the diagram related to V/III ratio and solid composition shrinks with increase of V/III ratio (increase of input partial pressure of NH_3). This is because the H_2 partial pressure produced by the decomposition of NH_3 increase at high V/III ratio (at high input partial pressure of NH_3).
