CARRIER TRAPPING INTO SINGLE GAAS QUANTUM WIRES STUDIED BY VARIABLE-TEMPERATURE NEAR-FIELD SPECTROSCOPY

The trapping of carriers into single GaAs quantum wires is studied by near-field luminescence and luminescence excitation spectroscopy with a spatial resolution of 250 nm. The formation of the investigated GaAs wires relies on a new growth mode in the preferential migration of Ga atoms on patterned (3 1 1)A GaAs surfaces. Near-field photoluminescen ce excitation spectroscopy allows for a separation of quantum wire and well absorption and gives evidence of slight potential barriers in th e vicinity of the quantum wire. At room temperature, carriers locally excited in the quantum well undergo real-space transfer over several m icrometers, pass the barriers and are trapped into the quantum wire vi a phonon emission. At temperatures below 20 K, real-space transfer thr ough the barriers is suppressed and only carriers generated in the vic inity of the quantum wire get trapped into bound states. (C) 1998 Else vier Science B.V. All rights reserved.