Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

With the observation of superconductivity at ambient pressure conditions in B doped Si in 2006 [1] and Ga doped Ge [2] the group-IV semiconductors become of interest for future information processing technologies like quantum computing.
To achieve the high doping levels needed for superconductivity non-equilibrium doping techniques like gas immersion laser doping or ion implantation and short term annealing are needed. Only the latter one is fully compatible to standard microelectronic technology. In a new approach we implanted a Ga concentration up to 11 at.% through a 30 nm SiO₂ cover layer into commercial Si and Ge wafers [3-6]. During annealing a thin superconducting Ga-rich nanolayer is formed at the SiO₂/semiconductor interface. These layers show promising superconducting properties (T_C = 7 K, B_C < 8 T, j_C < 50 kA/cm2).
Detailed microstructural investigations by means of XTEM and RBS/C will be discussed. Recent results show the adjustability of the superconducting properties. We are able to produce superconducting microstructures having a width of 3 µm and used the FIB to implement a Josephson junction as key element for a prospective SQUID.
[1] E. Bustarret et al., Nature 444 (2006) 465
[2] T. Herrmannsdörfer et al., Phys, Rev. Lett. 102 (2009) 217003
[3] R. Skrotzki et al., Appl. Phys. Lett. 97 (2010) 192505
[4] J. Fiedler et al., Phys. Rev. B 83 (2011) 214504
[5] J. Fiedler et al., Phys. Rev. B 85 (2012) 134530
[6] V. Heera et al., Appl. Phys. Lett. 100 (2012) 262602