Surface degradation mechanism of InP/InGaAs APDs

Bias-temperature tests of InP/InGaAs avalanche photodiodes have been conducted to evaluate long-term reliability at temperatures from 200-250 degrees C. Wearout -failure modes with a gradual increase in dark current occur at all testing levels. Failure analyses using the light-beam-induced current method suggest that the degradation is caused by local avalanche multiplication in the guard-ring periphery. A surface degradation mechanism is proposed, namely, positive charge accumulation in the passivation film above the guard-ring region, followed by local avalanche multiplication at the guard-ring periphery. A tentative activation energy of 1.7 eV is obtained for this failure mode, and the extrapolated median life exceeds 10/sup 10/ h in practical use.<
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