I've been using P-channel MOSFETs for high-side switches without problems in many Arduino projects (source connected to +5V and drain connected to the load). However, in a recent project I ran into an issue with this set-up.
The difference this time is that the load current is much smaller, 10uA rather than 20-100mA I usually switch, but it might temporarily shoot up to some mA for short bursts of time. I looked at the output voltage from the FET with an oscilloscope and when the gate goes low to turn on the FET, the output does not go up to 5V and stay there as I had expected, instead it seems to be fluctuating between 2-5V really fast or something like that. I tried connecting a 10Kohm resistor in parallel to my load but that did not solve the problem. Any ideas what could be causing this and what can be done to fix the issue?