Proton isolated In0.2Ga0.8As/GaAs strained-layer superlattice avalanche photodiode

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Abstract
We have fabricated the first proton isolated strained‐layer superlattice (SLS) avalanche photodiode. The grown In0.2Ga0.8As/GaAs p+n SLS structure was bombarded outside the active region with 220 keV protons to a total dose of 1×1015cm−2. These first nonoptimized devices exhibit a breakdown voltage of 23.5 V with a dark current density of 1.3×10−3A/cm2 at 90% of the breakdown voltage. The isolation is stable under annealing for 10 min at 350 °C. Uniform photoresponse is observed across the active region with two order of magnitude reduction in response occurring in the isolation region. A peak uncoated external quantum efficiency of 25% at 910 nm is observed with 10 V reverse bias and photocurrent multiplication is observed at higher bias values. These results demonstrate that proton isolation can be successfully applied to strained‐layer systems and can be incorporated in useful device structures.