In0.53Ga0.47As photodiodes grown on GaAs substrates have been fabricated and analyzed. The dislocation density in the InGaAs layer is 2×107 cm-2. A lowest dark current of 3.8×10-4 A/cm2 at 10 V bias is obtained, which is very stable during a bias‐temperature test of Vb=-10 V, T=175 °C, and t=100 h. The quantum efficiency is more than 85% at λ=1.3 μm. This device is expected to be practically used. The dark current has been successfully explained by the thermionic emission and thermionic field emission from traps at midgap. The diffusion length of holes in the InGaAs layer is explained by the recombination at dislocations with the finite recombination velocity of S∼104 cm/s.