Optical gain at low bias voltages in electrostatic-discharge-damaged silicon p-i-n photodiodes

The sensitivity of commercial p-i-n silicon photodiodes to electrostatic di scharges was determined by monitoring continuously electronic and optoelect ronic device properties during human body model step-stress tests. The devi ce degradation threshold pulse amplitudes ranging from 175 to 300 V for rev erse-bias stress and from 10 000 to 13 500 V for forward-bias stress were f ound, evidenced in all cases by an increase in the reverse-bias dark curren t. In the case of a forward-bias-stressed diode, however, we observed a sub stantial increase in the responsivity of the photodiode at low reverse-bias voltages after electrostatic-discharge-related degradation. The photocurre nt gain, which increased with decreasing light intensity and increasing bia s voltage, reached a saturation value exceeding 500 for low optical powers and a reverse-bias voltage of 10 V. Additionally it was-observed than the o pen-circuit voltage of the photodiode at a given light power is a more sens itive parameter for device degradation than the reverse-bias dark current a nd the short-circuit current.