On a sunny day (Fri, 9 Aug 2019 22:49:10 +0200) it happened Piotr Wyderski wrote in :
Yes, done that too:
The gate voltage at the JFET is enough to switch an IRLZ34N on / off.
Now all you need is some hot plutonium... for an RTG.
Magnifying lens, sun? Efficiency better than a solar panel?
Gotto try:-)