A planar InP/InGaAsP avalanche photodiode with a reduced junction curvature and lowp‐type doping was fabricated by Be+implantation through a photoelectrochemically etched InGaAs mask. A uniform gain as high as 15 was obtained without edge or surface breakdown. The device had a separated absorption and multiplication structure grown by vapor phase epitaxy. Then−‐InP top layer and guard ring conventionally used for planar devices were not needed. Two‐dimensional device modeling indicates that the reduced junction curvature and low doping can prevent edge breakdown and greatly suppress the surface field.