Highly doped Si and Ge formed by GILD (gas immersion laser doping); from GILD to superconducting silicon
Résumé
Gas Immersion Laser Doping (GILD) of silicon with boron has shown excellent performances in terms of junction depth, box-like profile, dopant concentration and activation. The study of the GILD process is extended to boron and phosphorus doping of silicon on insulator (SOI) and of relaxed Ge films epitaxied on Si or on SOI. The sheet resistances of Si and Ge doped films are measured as a function of the laser energy density and number of laser pulses. The dopant concentration profiles are measured by Secondary Ion Mass Spectrometry (SIMS) in the case of Ge on SOI. Experimental results on Ge show that GILD allows realizing doped layers with sheet resistances of ≈ 10 Ω/□ with nearly boxlike depth profiles, in the case of phosphorus, and of ≈ 40 Ω/□ with depth profiles peaked near the interface of the undoped Ge, in the case of boron. Finally we show that B doping by GILD allows reaching high enough dopant concentrations to make cubic silicon superconductive.