Stabilizing a GaN device

Hello Everyone!

I am working on an amplifier design and cannot stabilize a GaN discrete transistor. I have tried everything from resonance networks at the gate, to feedback but the device shows instability at 10 and 20MHz.

My design working bandwidth is from 1GHz to 5GHz. I was thinking of ignoring the stability, but this might mix up to the band of operation, especially if I plan to subject the device to modulation signals.

https://preview.redd.it/ykckh735pi8e1.png?width=810&format=png&auto=webp&s=b43a16f3acf97670a09a80223ad2d98ef1e89e9f

The screenshot above is the same transition with an RC tank at the gate employing C= 1pf and R = 300 ohms

I would appreciate it if someone could recommend stabilization techniques that might work.

Happy Holidays!!