Molecular Beam Epitaxy of Graphene on Ge(100) for Applications in Microelectronics and Optoelectronics

The integration of graphene in silicon technology using a Ge buffer layer is of high interest for both fundamental science and device applications. Various studies have investigated the growth of graphene on germanium by chemical vapor deposition, a technique that has unique advantages for applications but is hard to understand due to the interplay of interrelated and complex physicochemical mechanisms. To further understand the mechanisms of growth and the interactions between the germanium substrate and the deposited carbon atoms, we use an ultrahigh-vacuum molecular beam epitaxy chamber equipped with a carbon atomic source. The structures are characterized using scanning transmission electron microscopy and Raman spectroscopy, as well as capacitance and photocurrent spectroscopies. Our results show that the high deposition temperature yields high-quality graphene with good uniformity. Although Raman spectra reveal a prominent defect peak attributed to the underlying germanium substrate, the graphene/Ge(001) structure still exhibits promising electrical and optoelectronic properties. Notably, the observed quantum capacitance and photocurrent responses highlight its strong potential for applications in microelectronics and optoelectronics.