Reduced pore diameter fluctuations of macroporous silicon fabricated from neutron‐transmutation‐doped material

The precision of photo‐electrochemical etching of perfectly‐ordered macropores in single‐crystalline silicon is limited by pore diameter fluctuations due to doping variations of the starting wafer (striations). The doping variation originates from the rotation during crystal growth in the float‐zone or Czochralski process, respectively. Experimentally, variations of the pore diameter up to 7% can occur. These so‐called striations limit performance of possible applications of macroporous silicon. As doping inhomogeneities are the reason for the striations, uniformly doped silicon wafers by neutron transmutation doping were used for the first time. Photoelectrochemical etching of neutron transmutated silicon has been carried out and the pore diameter fluctuation has been reduced by about 40% compared to standard doped float‐zone wafers. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)