Long-distance diffusion of excitons in double quantum well structures

Area of Science:

• Condensed Matter Physics
• Materials Science
• Semiconductor Nanostructures

Background:

• Exciton dynamics in quantum wells are crucial for understanding energy and charge transport in semiconductor devices.
• Previous studies have explored exciton behavior, but detailed lateral diffusion measurements in specifically engineered double quantum wells remain an active area of research.

Purpose of the Study:

• To investigate and quantify the lateral diffusion of excitons at low temperatures in double quantum wells (DQWs) of varying widths.
• To establish that exciton motion is the primary mechanism for observed transport phenomena.
• To determine the relationship between exciton diffusion coefficients and quantum well dimensions.

Main Methods:

• Performed lateral diffusion measurements of excitons at low temperatures.
• Utilized double quantum well structures with controlled widths.
• Analyzed exciton lifetimes and diffusion distances (up to 500 micrometers).

Main Results:

• Excitons were observed to have long lifetimes (up to 30 microseconds).
• Exciton diffusion coefficients show a strong dependence on the width of the quantum well.
• The observed power law for exciton diffusion mirrors that of electron diffusion coefficients.

Conclusions:

• Confirmed that exciton motion is responsible for transport in these structures.
• The well width dependence of exciton diffusion suggests specific confinement effects.
• The similarity to electron diffusion power laws offers insights into charge carrier transport mechanisms in nanostructures.