Electrical and Optical Characterization of Surface Passivation in GaAs Nanowires

We report a systematic study of carrier dynamics in AlxGa1-xAs-passivated GaAs nanowires. With passivation, the minority carrier diffusion length (L-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 AlxGa1-xAs 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 X 10(3) to 1.1 X 10(4) cm.s(-1), and the minority carrier mobility mu is estimated to lie in the range from 10.3 to 67.5 cm(2) V-1 s(-1) for the passivated nanowires.