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Summary form only given.Near-field scanning optical microscopy (NSOM) and near-field photocurrent (NPC) detection are very attractive methods for studying surface characteristics of photoelectronic devices. The near-field laser light excites electron-hole pairs directly under the fiber tip in the semiconductor material. The photoexcited carriers are separated by p-n junctions and result in a photocurrent, while moving the sample or the tip to measure images. In this work, femtosecond time contrast NPC is applied for the first time, to our knowledge, to investigate the time response of spatially resolved surface impurities in a GaAsP diffusion-type photodiode.