Formation of nanovoids in high-dose hydrogen implanted GaN

The formation of nanovoids upon high-dose hydrogen implantation and subsequent annealing in GaN is investigated by transmission electron microscopy. The epitaxial GaN layers on sapphire were implanted at room temperature with H2+ ions at 100keV with a dose of 13×1016cm−2. Cross section transmission electron microscopy investigations revealed that nanovoids about 2nm in diameter had formed during hydrogen implantation at room temperature while large microcracks (∼150–200nm long) occurred upon annealing (1h at 700°C) leading to surface blistering. The nanovoids serve as precursors to the microcrack formation and are essential for the blistering process.