A method of passivating germanium that comprises providing a germanium material and carburizing the germanium material to form a germanium carbide material. The spinal fusion implants of the present invention may be relatively solid or hollow and may have surface roughenings to promote bone ingrowth and stability. An uplink subjective signal quality for each such handheld subscriber unit is determined based on a comparison of the stored test signal and the received test signal from the handheld subscriber unit. The holder base includes a pair of spaced cord ports, each cord port receiving a line part of a retractable cord that is engaged to the retractor mechanism. By introducing impurities that has a larger diffusion coefficient than the buried n+-layer, the collector layer can be formed on the buried n+-layer formed in common with other element regions, without any special masking. The filter blade has a control portion for controlling and adjusts the amount of light transmitted through the lens group.