Long-Distance Diffusion of Excitons in Double Quantum Well Structures

Abstract

In this Letter we report on lateral diffusion measurements of excitons at low temperature in double quantum wells of various widths. The structure is designed so that excitons live up to 30 micros and diffuse up to 500 microm. Particular attention is given to establishing that the transport occurs by exciton motion. The deduced exciton diffusion coefficients have a very strong well width dependence, and obey the same power law as the diffusion coefficient for electrons.

Exciton pattern generation in GaAs/AlxGa1−xAs multiple quantum wells

“…5 and shown schematically in Fig. 1, contains 20 periods of GaAs/AlGaAs multiple quantum wells (MQW) symmetrically positioned between 500Å AlGaAs barriers and 1000Å GaAs spacers.…”

“…3,4 These results are important examples of the ability to increase the lifetime of photogenerated direct-gap semiconductor charge carriers to microseconds through vertical and lateral charge separation. 5,6 Quantum transport measurements of high-mobility two-dimensional electron gases, for example, are usually performed in doped electron populations, since direct-gap semiconductor lifetimes do not permit photogenerated electrons to fully cool to the lattice temperature. With inhibited recombination, an ultracold electron population could be photogenerated, allowing dynamical spatial and temporal control via the exciting laser.…”

Anisotropic superfluidity of two-dimensional excitons in a periodic potential

“…A different option also exists: as a consequence of the anisotropy of sound, circular waves should become elliptic with the ratio between axes equal to C chemical potential 125 caused by a voltage applied to a region of the upper electrode 73,75 . The propagation of the wave can be observed then in a time-resolved luminescence experiment 126 . Another quantity we are interested in is the helicity modulus (24).…”

Exciton Transport Phenomena in GaAs Coupled Quantum Wells

“…Long lifetimes of the indirect excitons allow them to travel over macroscopic distances before recombination [Hagn et al, 1995;Butov and Filin, 1998;Larionov et al, 2000;Butov et al, 2002;Vörös et al, 2005;Ivanov et al, 2006;Gärtner et al, 2006;Alloing et al, 2011;.…”