I have made my experimentorture circuit, and right now I'm torturing a MOSFET with a positive voltage, feeding 0.3 uA of current into gate at 50% duty cycle (2.5 s of current, then 2.5 s of gate threshold measurement).
Gate threshold voltage (for Ids = 1 mA) was going down. Then it kinda stopped at around -0.5V. But I decided to no stop the process, and it started to go UP!!! Isn't it fascinating!
I have datalogging now, so I will post a plot when I finish it.
measurement in a mess...
UPDATE. The mosfet has changed back into enhancement mode... probably... , with gate voltage for 1 mA at about +0.25 V. It's too late now, so I have to stop the torture. I leave threshold to datalog overnight. With 13 SPS recording rate, it's going to be a big file.
UPDATE: the plot!
I started with 0.01 uA of torture current. No effect. Increased to 0.1 uA. Saw something. Increased to 0.3 uA. Now we are talking! Somewhere close to minimum, I was thinking to increase the current further, but changed my mind. Glad I did!
The wiggles on rising part are caused by me tweaking the torture current, which was reducing a little bit (the tweaks were like 0.28 -> 0.3 uA). The very fact it was reducing is interesting by itself, as it must be gate voltage going up.
I failed to stop the torture cleanly, oops! Nothing serious, though.