How to Measure Photodiode Dark Current

+ Femto / Picoammeters and Electrometers

Measure Reverse-Bias Dark Current

The test requires a photodiode mounted in an enclosed fixture so that no light reaches the device during measurement. A reverse-bias voltage is applied to the photodiode cathode while the resulting current is measured at the ammeter input. The measurement setup must support a voltage sweep and current acquisition over the expected low-current range.

For a representative silicon photodiode test, sweep the reverse-bias voltage from 10 mV to 5 V using 500 points and a fixed 20 pA current range. Use a 1 s measurement delay and a 1.2 s measurement period so that leakage and dielectric-absorption transients can settle before each reading. Display the current-voltage result on a logarithmic X-Y graph for quick examination.

Photodiode Dark Current Measurement Solution

The test requires a reverse-bias voltage sweep while the photodiode current is measured synchronously. The Keysight Electrometer / High Resistance Meter combines the voltage source and ammeter in one instrument, allowing the reverse-bias voltage to be swept while current is acquired at each point. For the example setup, the measurement uses a fixed 20 pA range, 500 sweep points from 10 mV to 5 V, and a 1 s measurement delay with a 1.2 s period. The instrument provides Graph View with logarithmic X- and Y-axis scaling for examining the current-voltage curve, and the measurement can be initiated from the front panel or remotely using SCPI commands.

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