Regrowth of GaN on Strain-relief porous GaN template fabricated by Anodized Alumina Oxide mask

Abstract

The growth of Gallium nitride on sapphire substrate generated a high density of threading dislocations in the order of ~108-109 /cm2. In this work, porous GaN template with different pore sizes was generated using Anodized Alumina oxide mask prepared by anodization with set voltage ranging from 40 V to 100V. Inductive coupled plasma etching generated porous GaN using the oxide mask. The etched pores have an estimated depth of 150 nm and the pores diameter range from 35 nm to 150 nm. Regrowth of GaN with embedded air voids provide a strain relaxed overgrown GaN layer with dislocation annihilation at the voids region. High resolution X-ray rocking curves at the symmetrical plane (002), (004) and (006) was obtained for the overgrown GaN demonstrate a significant reduction in FWHM for overgrown GaN on porous GaN template as compared to conventional GaN template. Dislocation density reduction estimated using Ayer model revealed an order of magnitude reduction of screw and mixed dislocation to higher order of 107cm-2 for overgrown on porous GaN with size of 70 nm to 100nm. Pits density counts which can be correlated to threading dislocations in the materials shows that the regrowth GaN samples on strain relief GaN has an order of magnitude lower pits density as compared to that conventional GaN sample.