Optical and structural properties of ln _xGa _1-xN films on tensile-strained GaN/Si(111) structures grown by using MOCVD

Due to the large differences in the lattice constants and the thermal expansion coefficients between GaN and Si, GaN growth on Si(111) substrates usually leads to initially high dislocation densities and cracks, We successfully deposited crack-free GaN films on Si(111) substrates by introducing AIN/GaN strain compensation structures and Si _xN _y dislocation masking layers. Moreover, we investigated the strong tensile stress in GaN films by using a temperature-dependent photoluminescence measurement. The In _xGa _1-xN films were grown on tensile-strained GaN/Si(111) structures by using metalorganic chemical vapor deposition (MOCVD) in a growth temperature range of 750 °C to 900 °C. Furthermore, the optical and the structural properties of the In _xGa _1-xN films were investigated by using photoluminescence measurement and high resolution X-ray diffraction. The In _xGa _1-xN bandgap energy depended on the In-composition, and the dependence could be fitted by using a larger bowing parameter of b = 4.5 eV in the Ga-rich region (x < 0.25). The results show that the higher band-gap bowing of In _xGa _1-xN epilayers on GaN/Si(111) structures may be a consequence of mechanisms such as a strain relaxation due to tensile strain and alloy disordering.