High-speed absorption recovery in quantum well diodes by diffusive electrical conduction

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Abstract
We present here picosecond time‐resolved electroabsorption measurements in GaAs quantum well p‐i‐n diode structures. While the dynamics of the vertical transport is not completely understood at present, our data reveal the importance of the ‘‘lateral’’ propagation of the photoexcited voltage pulse over the area of the doped regions. We propose a two‐dimensional ‘‘diffusive conduction’’ mechanism, which predicts a fast relaxation of the electrical pulse, with time constants ranging from 50 fs to 500 ps, determined by the size of the exciting spot, the resistivity of the doped regions, and the capacitance of the intrinsic region.