Conformal growth of III-Vs on Si: from low defect density materials to advanced devices

摘要

Conformal epitaxy is a growth technique capable of yielding very low dislocation density heteroepitaxial materials, such as III-V films on Si. In this technique, the III-V material grows parallel to the silicon substrate, from the edge of a previously deposited III-V seed, the vertical growth being stopped by an overhanging capping layer. As an example, conformal GaAs layers on Si, presenting dislocation densities below 10~5cm~(-2), have been obtaiend using selective chloride or hydride vapor phase epitaxy. These layers have then been used as high quality templates for subsequent vertical MBE regrowth of active structures. We first report on the integration of surface-emitting microcavity LEDs with their silicon drivers using this conformal growth technique. The high efficiency of the integrated LEDs and the negligible impact of the integration process on the drivers performance prove the efficiency of this procedure and its compatibility with advanced CMOS technology. Pseudomorphic GaAlAs/GaInAs HEMTs were also integrated on silicon substrates using this conformal technique: DC and RF characteristics highly improved compared to direct epitaxy on Si and close to reference ones on GaAs substrate were obtained. First relaisations of conformal epitaxy by MOCVD and of lateral devices on various types of substrates by modulating during conformal growth both doping and composition of the materials are finally presented.