Desoldering SMD transistors can get tricky. Their packages and PCBs are designed to sink a hot of heat so trying to remove them with hot air gun can result in destroyed PCB. I used a small CNC mill to selectively remove a broken GaN transistor. I used a 1mm burr with 15krpm and 60mm/min feed with 70μm passes. I went down until the solder pads were visible and cleaned the remaining bits with 120W soldering iron.