Photocapacitance spectroscopy of GaAs/AlGaAs multiquantum wells

Electron-hole generation in GaAs/AlGaAs quantum wells by illumination is shown to induce variations in the dynamical capacitance of multiquantum well capacitors. These variations monitored as a function of photon wavelength give a sensitive and unambiguous way to study excitonic resonances. It is shown that this photocapacitance spectroscopy technique leads to quantitative information on the product of the electron-hole pair density and their electrical polarizability. Assuming a simple theoretical model for electron-hole electrical polarizability, this method is applied to study the enhancement of exciton lifetime by a perpendicular electric field.