Annihilation of threading dislocations in strain relaxed nano-porous GaN template for high quality GaN growth

Abstract

Porous GaN subjected to heat treatment under in-situ MOCVD chamber annealing at 850 °C for 3 minutes has shown significant annihilation of threading dislocations and improvement of its optical quality. Similar phenomenon is not observed for the porous GaN samples annealed at lower temperatures. The annealing was done in a mixed of N2 and NH 3 ambient, which resulted in air-gap formation. Encounter of threading dislocations with the air-gap might cause them to bend horizontally and annihilate each other. Dark-field cross-section TEM image confirms the annihilation of threading dislocations within the porous/air-gap region. This dislocation density reduction causes a significant enhancement of the optical quality as shown by doubled Raman intensity of E2 phonon peak after the annealing as compared to the as-fabricated porous GaN. Because the fabricated porous GaN samples are already relaxed, no further strain relaxation is observed after annealing. Such a template is suitable for use in high quality GaN growth. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.