Imaging of defects in InGaAs/InP avalanche photodetectors created during electrostatic discharge stress

InGaAs/InP avalanche photodiodes failed during electrostatic discharge tests at voltages between 700V and 1000V. A failure analysis using photoluminescence imaging revealed the formation of star-like defects on the active area of the devices having an inhomogeneous photoresponse before the test. Differential phase contrast images of the damaged device showed metal migration from the guard ring towards the defect location. The reverse bias current after degradation increased for several orders of magnitude. For the degraded photodiodes with defects on the active layer a negative differential resistance has been observed in the forward current-voltage characteristics.