Threading dislocations annihilation in regrown GaN film on nanoporous GaN template

Abstract

Regrowth of GaN buffer layer on nanoporous GaN at different chamber temperature of 750 °C, 850 °C and 1000 °C are used to study the mechanism behind threading dislocations reduction in the GaN film subsequently overgrown. The growth of a 100 nm GaN buffer layer at 850 °C causes dislocations to bend into the underlying GaN and annihilated at the interface of GaN buffer/nanoporous GaN. Thermal treatment of nanoporous GaN in MOCVD growth chamber at 850 °C in NH3 and N2 ambient leads to the pinning of the threading dislocations at its surface edge steps by impurity -vacancy complexes of SiNx. The SiNx are formed by the impinging adatoms of NH3 which interact with Si dangling bonds at the subgrain boundaries of the nanoporous Si-doped GaN. When the nanoporous GaN sample undergoes rapid thermal annealing in N2 ambient, no effective filling of these voids are observed and dislocations density is not substantial reduced. Regrowth of GaN at 850 °C re-structured the nanoporous GaN, forming a SiNx complex at the voids or pores which pinned dislocation propagation. This explained the mechanism behind dislocation annihilation in regrown GaN on nanoporous GaN template with the use of additional interfacial GaN buffer layer. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.