Vapor phase In
xGa
1-xAs photodiodes were fabricated for compositions

. p
+-layers were made by Zn diffusion using ZnAs
2as a Source. Dark currents at half the breakdown voltage for

= 0.15, 0.17, and 0.31 were as low as those fabricated by liquid phase epitaxy. The planar structure is superior to a mesa structure with respect to dark current. Dark currents for various compositions were compared with theoretical estimation. Current multiplications in planar diodes with

were about 10 at the junction center and 200-300 at the periphery. Response time to 1.06-µm Nd: YAG mode locked laser pulses was measured to be about 250 ps.