Formation of Interfaces in Direct Bonded Heteropolytype SiC Structures Mediated with Liquid and Vapor Phase of Silicon

It is shown that heteropolytype silicon carbide structures can be obtained by direct bonding of wafers of different SiC polytypes by high-temperature treatment in vacuum. Heteroepitaxial 3C-SiC layers grown by the CVD method on a Si substrate were successfully transferred to 6H-SiC wafers. It was found that nanometer-thick bonding layers formed at the 3C-SiC/6H-SiC interface were the layers of recrystallized melt originating in a meltdown of the Si substrate of starting 3C-SiC/Si specimens. This example of transferring is a promising way for producing 3C-SiC/6H-SiC template for growing homoepitaxial 3C-SiC films of device quality. Feasibility of direct bonding of SiC single-crystal wafers in a silicon vapor environment also demonstrated. The motivation for these studies is development of prospective power devices on the base of 4H-SiC/6H-SiC heteropolytype junctions. It is shown that a necessary condition for bonding is а gap capable of providing vapor transport at the interface between the wafers. The gap was obtained by preliminary self-structuring of the surface of bonded SiC wafers with their annealing in vacuum.