Functionality of thermally hydrogen-passivated interfaces of oxidized crystalline arrays of Si nanowires on (100)Si
1 Department of Physics and Astronomy, KU Leuven - Celestijnenlaan 200D, 3000, Leuven, Belgium
2 imec - Kapeldreef 75, 3001 Leuven, Belgium
Received: 30 September 2013
Accepted: 25 May 2014
Electron spin resonance studies have been performed on arrays of single-crystalline Si nanowires (NWs), 375 nm long and of top diameter of about 5 nm, fabricated on (100)Si by top-down etching and final thinning by thermal oxidation in dry O2/N2 at . The SiO2/SiNW interfaces, showing a density of inherent electrically detrimental defects substantially exceeding that of standard technological (100)Si/SiO2, are of inferior electrical quality. An extensive study of the passivation kinetics in H2 and forming gas ambient reveals that, even under optimized conditions, the defect system cannot be inactivated to device grade (at best, improvement in H2), due to the excessive interface stress as exposed by the enhanced spread in activation energy for hydrogen passivation kinetics. The data reveal the inability, of intrinsic nature, to sufficiently suppress defects, preventing to reach device-grade functioning of solar cells using single-crystalline NW arrays on (100)Si in the current state of manufacturing.
PACS: 68.35.bg – Semiconductors / 81.07.Gf – Nanowires / 88.40.jj – Silicon solar cells
© EPLA, 2014