Kinetics of excitonic complexes on tunneling devices

Abstract

In this work we have investigated the effects of trion formation on the tunneling current from both experimental and theoretical viewpoints. We have measured the current-voltage characteristics and the quantum-well photoluminescence emission of $\mathrm{Ga}\mathrm{As}\text{\ensuremath{-}}{\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Al}}_{x}\mathrm{As}$ $n\text{\ensuremath{-}}i\text{\ensuremath{-}}n$ double barrier diodes. We have observed a preresonance shoulder in the current-voltage curve under high laser intensities associated with the formation of trions in the quantum well, which increase the number of free states in the resonant and excitonic levels, thus enhancing the tunneling mechanism. These excitonic complexes were detected through the photoluminescence spectra under bias. We have observed that the preresonance shoulder occurs under the same conditions for which a trion peak in the luminescence spectrum is present. This trion-assisted mechanism is terminated when neutral and charged excitons are dissociated either by thermal excitation or by scattering with free carriers in the quantum well. A phenomenological rate equation model has allowed us to confirm our assumptions on the effect of trion formation on the charge transport.