Hydrogen etching of GaN and its application to produce free-standing GaN thick films

► The morphology of GaN etched in hydrogen at different temperatures is studied. ► H2 etching has controllable etching directions. ► The activation energy of the rate-limiting step of hydrogen etching is 3.7 eV. ► A 320 μm-thick GaN layer has self-separated from the underlying sapphire substrate.