A planar InP/InGaAsP heterostructure avalanche photodiode

A new guard-ring structure for InP/InGaAsP heterostructure avalanche photodiodes (APD's) is presented. The guard ring consists of a linearly graded junction formed by beryllium ion implantation and two-step InP layers having different carrier concentrations (n
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and n-layers grown on an InGaAsP layer). A planar InP/InGaAsP avalanche photodiode having this guard ring has a maximum avalanche gain of 110 at an initial photocurrent of 0.35 µA. The effectiveness of the guard ring is clearly discernible from the spot-scanned photoresponse of the diode.