title: Relative influence of surface states and bulk impurities on the electrical properties of Ge nanowires.
abstract: We quantitatively examine the relative influence of bulk impurities and surface states on the electrical properties of Ge nanowires with and without phosphorus (P) doping. The unintentional impurity concentration in nominally undoped Ge nanowires is less than 2 x 10(17) cm(-3) as determined by atom probe tomography. Surprisingly, P doping of approximately 10(18) cm(-3) reduces the nanowire conductivity by 2 orders of magnitude. By modeling the contributions of dopants, impurities, and surface states, we confirm that the conductivity of nominally undoped Ge nanowires is mainly due to surface state induced hole accumulation rather than impurities introduced by catalyst. In P-doped nanowires, the surface states accept the electrons generated by the P dopants, reducing the conductivity and leading to ambipolar behavior. In contrast, intentional surface-doping results in a high conductivity and recovery of n-type characteristics.
authors: Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA.
authors: Shixiong
authors: S
authors: Zhang
authors: Eric R
authors: ER
authors: Hemesath
authors: Daniel E
authors: DE
authors: Perea
authors: Edy
authors: E
authors: Wijaya
authors: Jessica L
authors: JL
authors: Lensch-Falk
authors: Lincoln J
authors: LJ
authors: Lauhon
mesh_terms: D004553:Electric Conductivity; D004583:Electrons; D005857:Germanium / Q000737:chemistry*; D008422:Materials Testing; D036103:Nanotechnology; D053770:Nanowires / Q000737:chemistry*; D010316:Particle Size; D010758:Phosphorus / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature
chemical_list: D005857:Germanium; D010758:Phosphorus