Observation of Charge Transport by Negatively Charged Excitons

We report transport of electron-hole complexes in semiconductor quantum wells under applied electric fields. Negatively charged excitons (X-), created by laser excitation of a high electron mobility transistor, are observed to drift upon applying a voltage between the source and drain. In contrast, neutral excitons do not drift under similar conditions. The X-mobility is found to be as high as$6.5 \times 10^4\>cm^2\>V^{-1}\>s^{-1}$. The results demonstrate that X-exists as a free particle in the best-quality samples and suggest that light emission from opto-electronic devices can be manipulated through exciton drift under applied electric fields.