Germanium p-n Junctions by Laser Doping for Photonics/Microelectronic Devices

A method of forming germanium p-n junction by laser doping is demonstrated. Low bulk and surface leakage current density of 5.4 mA/cm 2 and 2.0 μA/cm, respectively, were obtained. The leakage current density was comparable with the diodes formed by rapid thermal diffusion, but approximately two orders of magnitude lower than the diodes formed by ion implantation. The performance of the laser doped junction in photonic devices was demonstrated through the fabrication of 130-μm diameter photodetector, which showed a responsivity of 0.46 A/W at 1.55-μm wavelength at 0 V bias and a -3-dB bandwidth of 190 MHz.