Why does gallium nitride allow an AESA radar to be more powerful than a radar with elements made of gallium arsenide?

AESA (Actively Electronically Scanned Array) radars use thousands of individual transmit/receive elements to create a radar. All in service AESAs use gallium arsenide as the material in the t/r elements. It is said that gallium nitride allows a tenfold increase in the power emitted by these elements? What allows GaN to emit so much more radio frequency energy than GaAs?