Thermodynamic study on compositional instability of InGaN/GaN and InGaN/InN during MBE

Abstract Thermodynamic analyses were carried out to understand influence of lattice constraint from GaN and InN substrates on relationship between solid composition x of In x Ga 1− x N films and input mole ratio R In (= P In 0 /( P In 0 + P Ga 0 ) where P i 0 is the input partial pressure of element i ) during molecular beam epitaxy. The calculated results suggest that compositional unstable region is found at small R In region for InGaN on InN while that for InGaN on GaN can be seen at large R In region at higher temperatures. This implies that InN-rich thin films are possible to form on InN substrate though it is difficult to form on GaN substrate.