Investigations of floating guard structures in a planar InGaAs/InGaAsP/InP avalanche photodiode

Abstract

We have experimentally investigated the role of floating guard structures to suppress the peripheral electric field in a planar InGaAs/InGaAsP/InP avalanche photodiode. The floating guard rings (FGR's) were analyzed in a systematic method, and floating guard dots (FGD's) were employed for the first time. It was confirmed from the photocurrent maps that the essential role of the FGR's was to disperse the curved equipotential lines at the lateral junction periphery and to give a low-field route for a carrier beneath the FGR's. The optimum guard ring condition was found. The FGD's showed a prospective, not yet optimized, result in the photocurrent map.