Planar avalanche photodiode with a low-doped, reduced curvature junction

A planar InP/InGaAsP avalanche photodiode with a reduced junction curvature and low p-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. The n−-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.