Ultrafast photodetection in the quantum wells of single AlGaAs/GaAs-based nanowires

N. Erhard, S. Zenger, S. Morkötter, D. Rudolph, M. Weiss, H. J. Krenner, H. Karl, G. Abstreiter, J. J. Finley, G. Koblmüller, A. W. Holleitner

Nano Letters 15 6869-6874 (2015)

We investigate the ultrafast optoelectronic properties of single Al0.3Ga0.7As/GaAs core–shell nanowires. The nanowires contain GaAs-based quantum wells. For a resonant excitation of the quantum wells, we find a picosecond photocurrent which is consistent with an ultrafast lateral expansion of the photogenerated charge carriers. This Dember-effect does not occur for an excitation of the GaAs-based core of the nanowires. Instead, the core exhibits an ultrafast displacement current and a photothermoelectric current at the metal Schottky contacts. Our results uncover the optoelectronic dynamics in semiconductor core–shell nanowires comprising quantum wells, and they demonstrate the possibility to use the low-dimensional quantum well states therein for ultrafast photoswitches and photodetectors.