Molecular beam epitaxy of high-quality GaAs on Si (001) by multi-time thermal cycle annealing

Heteroepitaxy of GaAs on Si enables well-functioning III–V semiconductor lasers integrated onto silicon, solving the issue of lacking purely silicon-based light sources. Since GaAs has been the key material in many III–V laser structures, the Si-based GaAs epilayer should be of high quality which requires a low surface roughness and dislocation density. Herein, we demonstrate a high-quality heteroepitaxy of 1.84 μm GaAs on Si (001) substrates by molecular beam epitaxy. By virtue of multi-time thermal cycle annealing, the surface roughness was reduced to 1.74 nm within a scan area of 10 × 10 μm2, and the measured threading dislocation density was as low as 6.87 × 106/cm2. Periodic interfacial misfit dislocation arrays were found at the GaAs/Si interface with a misfit-dislocation-spacing distance of 9.6 nm. The formation of these arrays is attributed to the usage of thermal cycle annealing which makes near-interface TDs form into in-plane misfit dislocations. The demonstrated epitaxy scheme of growing such high-quality GaAs/Si virtual substrates provides a feasible way to fabricate III–V semiconductor lasers with enhanced performances.