EXAFS studies of plasma-enhanced MBE grown Group III-Nitrides

We have been studying the structural properties of Group III-Nitrides on Si substrates. We have shown from X-ray data that alloys of (AlGa)N and (InGa)N can be grown by plasma enhanced molecular beam epitaxy on oxidised (100) Si substrates with good control of the composition, over the entire range from InN to AlN. The composition of the alloys deduced from electron probe microanalysis data agree well with those from X-ray measurements assuming Vegard's law is valid for both alloy systems. SIMS studies show that the film composition is uniform in depth. EXAFS studies show no evidence for spinodal decomposition over the entire composition range for the (InGa)N alloys and indicate a monotonic variation in lattice parameter with increasing In mole fraction.