The key issues for growing III-V compound layers, free of structural defects, on Si substrates are clarified. The technologies for overcoming the fundamental problems have been developed. As a result, it has been clarified that dislocation-free III-V-N alloys can be grown on Si substrates whose lattice constants are matched to those of Si. Device structures of the GaAsPN/GaPN quantum well structure and the Si/GaPN/Si structure have been successfully grown on a Si (100) substrate covered with a thin GaP initial layer. The grown layers and hetero-interfaces contained no threading dislocations and no misfit dislocations, respectively. Neither stacking faults nor anti-phase domains were observed. A key issue for application to novel devices is the increase in nitrogen composition without degrading optical and electrical properties.