Controlled axial and radial Te-doping of GaAs nanowires

• Published in: Journal of applied physics Vol. 112; no. 5
• Main Authors: Salehzadeh, O., Kavanagh, K. L., Watkins, S. P.
• Format: Journal Article
• Language: English
• Published: 01.09.2012
• Subjects: Cooling; Gallium arsenide; Gallium arsenides; Gallium base alloys; Gold; Nanostructure; Nanowires; Scanning electron microscopy
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4751988

Tellurium (Te)-doping of Au-catalyzed GaAs nanowires (NWs) grown by metalorganic vapor phase epitaxy (MOVPE) via the vapor-liquid-solid (VLS) mechanism is presented. Electrical measurements were performed inside a scanning electron microscope by contacting a tungsten nanoprobe to the Au end of individual NWs grown on a heavily n-type GaAs substrate. Rectifying current-voltage (I-V) characteristics are observed due to the formation of a junction at the Au nanoparticle (NP)/NW interface. The electron concentration ne and contact barrier heights, φ0b, were determined from the analyses of these characteristics. As expected, φ0b increased (from 0.63 ± 0.03 eV to 0.71 ± 0.02 eV) with decreasing Te-precursor flow rate, corresponding to a decrease in ne from (9 ± 1) × 1017 cm−3 to (1.5 ± 0.5) × 1017 cm−3. Meanwhile, undoped NWs had space-charge-limited characteristics. There was a large influence of the residual gallium (Ga) in the NP, on barrier properties, controlled by the group V precursor flow (on or off) during the cooling of the NW sample at the end of the growth process. With the group V flow off during cooling, a decrease in φ0b from 0.79 ± 0.04 eV to 0.63 ± 0.03 eV is observed consistent with a higher Ga alloy concentration in the NP, confirmed by energy dispersive spectroscopy measurements. We also demonstrate the fabrication of core/shell, undoped/Te-doped, GaAs NWs with very high Te doping (∼1019 cm−3).