Photocurrent spectroscopy of confined quantum states in single quantum well tube nanowire devices*

We investigate optical transitions in GaAs/AlGaAs core-multishell nanowires Quantum Well Tubes (QWT) devices using photocurrent spectroscopy (PC) at low temperature (10K). The GaAs quantum well layer was embedded inside a thick AlGaAs shell surrounding a 50 nm diameter GaAs NW. The single nanowire devices were fabricated by standard photolithography followed by deposition of Ti (20nm)/Al (500nm) metal contacts on either end the nanowire. We present results for two sets of quantum well tubes having quantum well widths of 8nm and 4nm. The QWT nanowire devices exhibit very low (sub pA) dark current and are extremely photosensitive. PC measurements of the QWT devices exhibit photocurrent peaks corresponding to excitons confined to the GaAs core as well as ground and excited states of electrons and holes confined to the quantum well tube, and also in the barrier. Comparisons of the PC spectra with PL and PLE measurements on the same devices show that the peaks associated with the PC spectra show a close correspondence.