Thermal Studies of Si-Ge Heterostructure Interfaces by Film-Wafer Bonding*

For a twist grain boundary (GB), previous studies suggest that interfacial thermal resistance (R_K) has a strong dependence of the crystal misorientation at the GB. For heterostructure interfaces, the interfacial atomic structures and phonon transport are more complicated. In this study, Si thin films are hot pressed onto Ge substrates to represent a Si-Ge heterostructure interfaces formed in SiGe nanocomposites. The interfacial R_K is measured using an offset 3ω method for varied crystal orientations. GB strain is also measured with Raman spectroscopy to reveal its connection with R_K, along with interfacial structure characterization by transmission electron microscopy. Our detailed interfacial thermal studies can provide important guidance for interface engineering to tune the heat transport inside a material or device.