We show that a significant enhancement of the direct band gap photoluminescence can be achieved at room temperature in bulk Ge and Ge-on-insulator heavily n-doped by gas immersion laser doping. The photoluminescence signal from bulk Ge and Ge-on-insulator increases with the donor concentration. An enhancement factor of 20 as compared to the undoped material is achieved near the 1550 nm wavelength for active dopant concentrations around 5 ϫ 10 19 cm −3. These results are supported by calculations of the Ge spontaneous emission spectrum taking into account the doping effect on the electron distribution in the direct and indirect conduction band valleys.

International audienceWe report on a detailed analysis of the superconducting properties of boron-doped silicon films grown along the 001 direction by gas immersion laser doping. The doping concentration c(B) has been varied up to similar to 10 at. % by increasing the number of laser shots to 500. No superconductivity could be observed down to 40 mK for doping level below similar to 2 at. %. The critical temperature T(c) then increased steeply to reach similar to 0.6 K for c(B) similar to 8 at. %. No hysteresis was found for the transitions in magnetic field, which is characteristic of a type II superconductor. The corresponding upper critical field mu(o)H(c2) (0) was on the order of 1000 G, much smaller than the value previously reported by Bustarret et al. [E. Bustarret et al., Nature (London) 444, 465 (2006)]

No abstract