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Measure diode at low current with pulse sweep Log

Model 2651A
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yudong123
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Joined: August 27th, 2018, 9:35 am
Country: United States

Measure diode at low current with pulse sweep Log

Post by yudong123 » October 31st, 2018, 2:46 pm

Hi,

I am trying to measure a diode at low current range with 2651A. I am using KIPulse command from manual.
f1, msg1 = ConfigPulseIMeasureVSweepLog(smua,0,1e-9,1e-6,1,0.0001,0.01,60,{v = smua.nvbuffer1, i = smua.nvbuffer2},1)

The reading I got is a mess and current readings were totally wrong. I was expecting a straight line in the plot with log y axis.
I set the current source and measurement range at 1e-6, and the voltage range at 1V.
So my question is, is it possible to get a nice result with ConfigPulseIMeasureVSweepLog() function at low current range with 2651A?

Thanks,
Yu

Andrea C
Keithley Applications
Keithley Applications
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Joined: October 15th, 2010, 10:35 am
Country: United States
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Re: Measure diode at low current with pulse sweep Log

Post by Andrea C » November 1st, 2018, 11:13 am

With any pulse mode testing you have to consider the actual pulse shape and the effect of that on the measurements.
For example, if you sample before the pulse has become settled, the measurement will be invalid.

In your specific case, you are asking for rather low levels of pulsed current (1nA or less) to occur within a 100usec pulse width.
I think it will be unlikely that system capacitance can charge to final value within that time if only 1nA of current or less is being forced. System capacitance will be due to cables and junction capacitance of the diode DUT.

Try significantly longer pulses. Do you have a scope? Hook the scope probe to the Guard connection on the SMU to see the voltage response timing without having the input R of the scope probe affect the current to the DUT.

Or better yet, joule heating is unlikely at these power levels. Can you instead use a conventional DC staircase sweep?

yudong123
Posts: 5
Joined: August 27th, 2018, 9:35 am
Country: United States

Re: Measure diode at low current with pulse sweep Log

Post by yudong123 » November 1st, 2018, 11:33 am

Hi,
Thank you very much for the reply!! I think that is exactly the issue of my setting. I went with SweepVLogMeasureI() function and result came back fine. However, lets say if I need to measure a sweep from 1 nA to 1 mA, the SweepVLogMeasureI() function will only define the i range once and it will be 1mA. Does this mean I actually need to break the range (1nA - 1mA) into smaller ranges, and use SweepVLogMeasureI() for each of the range?

Also I was using labview through ethernet communication to control the 2651A. I attached my vi here. I noticed that when I use TSB builder and type in
"SweepILogMeasureV(smua,1e-9,1e-7,0.1,10)" and "printbuffer(1,10,smua.nvbuffer1)" in the console, everything works our just fine. But when I run my vi, I kept getting overflow readings from the buffer. I am suspecting that its the problem of the timing, but I am not sure how to fix it..

Thanks,
Yu
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Keithley2651AsweepIDC.vi
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