Souring 0A current and get 1.5V on my doide

Hi there,

We were testing a diode using probers. Once we landed the probers on the device, the voltage reading from 2636B is jumping around between 0V to 2V. (finding1)
In order to troubleshoot, we sourced 0A with 1.5A range and got 1.5V reading on the device. When sourced 0A with 1uA range, the voltage reading is 0.2V. (finding2)
When we were souring 0V, 2636B shows nA/pA, which is normal.
Do you have any explanation for it?
Thanks,
EC

Looking at the source spec for the 1.5Amp range, you could have as much as +/-4mA of current and still be within spec for source value of 0Amps.
In contrast, when using 1uA range to source 0A, the error budget drops to +/-700pA.

If wanting the SMU to behave like a volt meter, in general, use the most sensitive range available to source the 0Amps.  Set the corresponding voltage compliance limit to a value larger than the DUT can produce.  Measure V.


For your finding1, what was the state of the SMU before landing the probes?  Was it already in Force I, Measure V?  Was blue light on?

Thanks for the reply regarding the finding2.

For the finding1, the 2636B is off with no blue light on. I was thinking there may be a leakage current due to no proper grounding? Or due to 60Hz noise from environment?

Best,

EC

For your finding1 topic:  when blue light is off, if the SMU is in default output off config, then it is behaving as a 0V source with ability to source or sink 1mA.
This should result in 0V starting point.
When you say the voltage was jumping around 0 to 2V, what was the condition of the SMU then?

Any chance there was an open circuit due to probing issue?

NOTE:  for PN junction, if using SMU to force current and forward bias the diode, it is very much possible to trap charge on the PN junction when the SMU returns to 0Amps and the blue light is still on, especially if using a low source range.
Suppose you force current with a 3V limit.  When you return to 0Amps, the SMU has no trouble to allow as much as +/-3V.
This should be fairly steady, but could decay due to leakage in the device, cables or allowed offset of the source range.
You can bleed off the trapped charge by turning output off OR by temporarily setting the voltage limit to smaller value.