Electrical and Optical Characterization of Surface Passivation in GaAs Nanowires

We report a systematic study of carrier dynamics in Al_<i>x</i>Ga_1–<i>x</i>As-passivated GaAs nanowires. With passivation, the minority carrier diffusion length (<i>L</i>_diff) increases from 30 to 180 nm, as measured by electron beam induced current (EBIC) mapping, and the photoluminescence (PL) lifetime increases from sub-60 ps to 1.3 ns. A 48-fold enhancement in the continuous-wave PL intensity is observed on the same individual nanowire with and without the Al_<i>x</i>Ga_1–<i>x</i>As passivation layer, indicating a significant reduction in surface recombination. These results indicate that, in passivated nanowires, the minority carrier lifetime is not limited by twin stacking faults. From the PL lifetime and minority carrier diffusion length, we estimate the surface recombination velocity (SRV) to range from 1.7 × 10³ to 1.1 × 10⁴ cm·s^–1, and the minority carrier mobility μ is estimated to lie in the range from 10.3 to 67.5 cm² V^–1 s^–1 for the passivated nanowires