Analysis and Characterization of p-n Junctions Fabricated by Low-Power Focused Ion Beam

The properties of implanted p⁺ layer and shallow p-n junctions fabricated using 20 -keV Ga⁺ focused ion beam (FIB) into crystalline Si substrates are investigated. From LSS theory, the junction depth is projected to be 42 nm. Raman spectroscopy measurement shows that the damages from implantation at the p+ layer are completed repaired by annealing at 800 degC for 30 minutes when the dose is 1x10¹⁴ /cm², but the damages still remain when the dose is 1 x10¹⁶ /cm². The current-voltage characteristics of p-n junctions show four small regions inside the forward bias region and rising saturation current in the reverse bias region as predicted in theory. At the very small forward bias region, from 0 V to 0.16 V, the current increases linearly with the bias voltage. After compensation for series resistance of 0.63 Omega-cm², the ideality factor at the forward bias region dominated by diffusion current is 1.60. At the reverse bias region, the saturation current increases with the bias voltage. The high level of saturation current and the deviation of ideality factor from theory are considered to be the results of large amount of defects, which remained even after annealing process.