Some Considerations Concerning the Detection of Excitons by Field Ionization in a Schottky Barrier

Abstract

The possibility of Bose-Einstein condensation of excitons in semiconductors and/or their superfluid transport are long-standing, still controversially discussed problems. In a recent series of experiments by E. Fortin and coworkers [1–3] [phys. stat. sol. (b) 191, 345 (1995); Phys. Rev. Lett. 77, 896 (1996); and Proc. Internat. Conf. Exciton Processes in Condensed Matter, World Scientific, Singapore 2000, respectively], (para-)excitons in Cu2O have been detected electrically by their field ionization in a Schottky barrier. We analyze the electric field in the Schottky barrier and its screening by the holes remaining after field ionization and find serious screening and saturation effects of this Schottky-barrier exciton detector under the excitation conditions of the experiment. These findings make a reinterpretation of the data very likely.