Coaxial core-shell GaAs/AlGaAs nanowires are promising for high-speed devices, light-emitting diodes, and photonic device applications. The surrounding shell provides not only passivation of surface states, but also a parallel transport channel. With large mobility difference and band offset, competition between electrons transferred from the GaAs core to AlGaAs shell and those transiting along the core results in negative differential resistance (NDR) in the photocurrent which can be modulated using electric field, photon energy, and photon flux. For rational device design, an understanding of carrier transport and interface band structure is necessary.
We present our recent results on probing carrier transport in a single core-shell nanowire by electron beam induced current (EBIC) which has a high lateral resolution of ~10 nm. Spatial profiles from devices under applied electric field resolve drift component in a coupled drift-diffusion transport. We report on axial position- and bias voltage-dependent differences in carrier transport along parallel conduction channels in single nanowire device using EBIC. We also use photocurrent spectroscopy to directly measure the band alignment at nanowire interface. Together with atom probe tomography, an accurate model of interface electron transfer can be determined.
Work at Drexel supported by NSF (DMR 0907381) and the US Dept of Education under the GAANN-RETAIN program (P200A100117).
G. Chen, E. M. Gallo, O. D. Leaffer, T. McGuckin, P. Prete, N. Lovergine, and J. E. Spanier, “Tunable Hot-Electron Transfer Within a Single Core-Shell Nanowire,” 107, 1-5, (2011).
G. Chen, G. Sun, Y. J. Ding, P. Prete, I. Miccoli, N. Lovergine, H. Shtrikman, P. Kung, T. Livneh, and J. E. Spanier, “Direct measurement of band edge discontinuity in individual core-shell nanowires by photocurrent spectroscopy,” 13, 4152-7, (2013).