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A small mesa structure (10 μm × 10 μm, 15 nm thick) of intrinsic Josephson junctions in Bi2Sr2CaCu2o8+δ is employed to observe the tunneling characteristics and the superconducting gap magnitude by short pulse technique (short pulse interlayer tunneling spectroscopy). In the measurement on 60 ns time scale, the effect of self-heating is almost negligible in the sample, whose resistivity is as small as 10 Ωcm. In slightly overdoped region, the maximum Josephson current density increases from 0.85 to 2.1 kA/cm2 with increasing doping level. The superconducting gap magnitude 2Δ decreases from 62 to 37 meV with increasing doping level. The value for 2Δ/kBTc decreases from 8.3 to 5.2 with increasing doping level. These values in slightly overdoped region are smaller than those in optimum and underdoped region.