Microfabrication of Black Ge by SF6/O2-and C4F8-based Deep Reactive Ion Etching

We fabricated black Ge with numerous needlelike microstructures by SF6/O2- and C4F8based deep reactive ion etching and measured the regular reflectance in the ultraviolet-to-nearinfrared range, thermal radiation properties, and electrical resistance for electrode applications. The regular reflectance of black Ge was very low in the range of 250 nm-2.5 mu m. The emissivity of the black Ge surface was observed to be the same as that of a carbon plate. We found that the scallops on the sidewalls of the microstructures also contributed to the low reflectance. Furthermore, the black Ge electrode had a lower resistance than a planar Ge electrode. The black Ge electrode, which has an increased surface area of Ge with numerous needlelike microstructures, has high emissivity, antireflectivity and low resistance, and we consider that it is useful for application to device fabrication utilizing these properties.