Formation of nanovoids/microcracks in high dose hydrogen implanted AlN

Aluminium nitride (AlN) epitaxial layers grown on sapphire were implanted with 100 keV hydrogen, H2 + ions with doses in the range of 5 × 1016 cm–2 to 2.5 × 1017 cm-2 and subsequently annealed at temperatures up to 800 °C in order to observe the formation of surface blisters. The implantationinduced damage in AlN was analyzed by cross-sectional transmission electron microscopy, which revealed a band of defects extending from 330–550 nm from the surface of AlN. Higher magnification TEM images showed the formation of nanovoids that are distributed in the damage band. Upon annealing these nanovoids agglomerate leading to the formation of microcracks. Due to the overpressure of hydrogen trapped in the microcracks, surface blisters are eventually formed in the hydrogen implanted AlN.