Large bandgap bowing of in_xGa_1-xN films and growth of blue/green in_xGa_1-xN/GaN MQWs on highly tensile strained GaN/Si(111) hetero structures

In_xGa_1-xN films and In_xGa _1-xN/GaN multiple quantum wells (MQWs) were grown on highly tensile strained GaN/Si(111) structure by MOCVD. Due to the large difference of lattice constant and thermal expansion coefficient between GaN and Si, GaN growth on Si(111) substrate usually leads to an initially high dislocation density and cracks. We demonstrate the low dislocation density and crack-free GaN films grown on Si(111) substrate introducing an AIN/GaN strain compensation layer and Si_xN_y dislocation masking layer. The Raman shift of E ₂ phonon peak of GaN films on Si(111) substrate indicate the strong tensile stress (0.474 GPa). The In_xGa_1-xN bandgap energy depended on In-composition, which can be fitted by a larger bowing parameter of b = 4.5 eV in Ga-rich region (x < 0.25). Also, crack-free In _xGa_1-xN/GaN MQWs with blue and green emissions were demonstrated.