During my RF design career with Motorola and Raytheon (formerly Magnavox), I designed many military and commercial solid-state RF power amplifiers ranging from 1 W to 1 KW from 30 MHz to 2 GHz using constant envelope waveforms (FM, for example) and non-constant envelope waveforms (OFDM, for example) employing bipolar junctions transistors, vertical MOSFETs, LDMOS and ultimately GaN.
Watch this link for RF power amplifier papers.
Impact of SWR on Eff of PA
Design Issues for a VHF-UHF Solid State RF Power Amplifier
Characterizing an RF Power Amplifier with Pin and Pout Data