Phase separation in InGaN thick films and formation of InGaN/GaN double heterostructures in the entire alloy composition

We report the growth of InGaN thick films and InGaN/GaN double heterostructures by molecular beam epitaxy at the substrate temperatures 700-800 degrees C, which is optimal for the growth of GaN. X-ray diffraction and optical absorption studies show phase separation of InN for InxGa1-xN thick films with x>0.3. On the other hand, InxGa1-xN/GaN double heterostructures show no evidence of phase separation within the detection capabilities of our methods. These observations were accounted for using Stringfellow's model on phase separation, which gives a critical temperature for miscibility of the GaN-InN system equal to 2457 K. (C) 1997 American Institute of Physics.