Measurements of the electron-hole binding energy in coupled GaAs/AlGaAs quantum wells

Abstract

We report the first measurements of the electron-hole binding energy for spatially indirect excitons. Working with a system of coupled 9.2 nm and 5.8 nm GaAs quantum wells, we observe the variation in the binding energy as the system is electrically tuned from type I (large electron-hole overlap) to type II (vanishing electron-hole overlap). Under type II conditions, a bound state persists, with binding energy as large as 3 meV.