Dislocation density reduction in heteroepitaxial III-V compound films on Si substrates for optical devices

The reduction of dislocation density in heteroepitaxial III-V compound films on Si substrates has been studied using MOCVD (Metal-Organic Chemical Vapor Deposition). High-quality GaAs films on Si, with a dislocation density of about 10⁶ cm⁻², have been obtained by combining strained-layer superlattice insertion and thermal cycle annealing. Reduction of dislocation density in the III-V compounds on Si is discussed based on a simple model, where dislocation annihilation is assumed to be caused by dislocation movement under thermal and misfit stress. As a result of dislocation density reduction, high-efficiency GaAs-on-Si solar cells with total-area efficiencies of 18.3% (AM0) and 20% (AM1.5), and red and yellow emissions from InGaP-on-Si light-emitting diodes have been realized. Moreover, future prospects of heteroepitaxy of III-V compounds on Si are also discussed.