Scanning capacitance microscopy detection of charge trapping in free-standing germanium nanodots and the passivation of hole trap sites

An array of freestanding germanium (Ge) nanodots was fabricated on a highly doped silicon substrate using an anodic alumina membrane as an evaporation mask. Approximately half of the Ge nanodots exhibit contrast reversal and hole trapping characteristics during scanning capacitance microscopy (SCM) measurements, as shown by a negative peak in the SCM differential capacitance (dC/dV) versus probe tip-to-substrate bias profile. The disappearance of the negative dC/dV characteristic peak after forming gas anneal at 450 degrees C show the complete passivation of the hole trap sites by hydrogen. This is a demonstration on the spectroscopic detection of hole trapping in Ge nanodots and hydrogen passivation of hole trap sites using SCM. Partial passivation of electron trap sites after the relatively low temperature forming gas anneal was also observed as compared with complete passivation of hole trap sites. This suggests that hole traps sites are possibly located at or closer to the surface of the Ge nanodots as compared to electron traps which may be located deeper within the Ge nanodots. (C) 2008 American Institute of Physics.