Spiral growth and formation of stacking faults and vacancy islands during molecular beam epitaxy of InN on GaN(0001)

Abstract

The surface morphology and atomic structure of InN grown on the Ga-rich GaN(0001)-pseudo (1 × 1) structure is studied by scanning tunneling microscopy. Spirals are formed as a result of screw dislocations emerging at the surface to relieve the strain from the lattice mismatch. Two additional types of strain relaxation mechanisms are also found, both due to the incorporation of excess Ga atoms from the starting pseudo (1 × 1) surface into the growing films. For films below 8 nm where the Ga concentration is larger than 7%, the formation of stacking faults at the InN/GaN interface produces a triangular network on the surface. The density of the stacking faults is found to decrease with film thickness and with the gradual consumption of the Ga atoms, and the network is therefore no longer observable above a critical thickness that varies from 8 to 10 nm. Instead, vacancy islands, one atomic layer deep, are formed to relieve the stain near the surface region. These results provide atomic scale insights into the interplay between the surface morphology and strain relaxation during the epitaxial growth of highly lattice mismatched InN/GaN heterostructures.

Imaging defects in vanadium(iii) oxide nanocrystals using Bragg coherent diffractive imaging

“…The nature of the dislocations identified in BCDI may provide some insight into the stark contrast between the particle identified in the BCDI measurement and the particles observed with optical and AFM measurements. The presence of a partial dislocation implies the existence of a stacking fault near the base of the crystal; stacking faults have been shown to reduce the energy in thin films, 42 but were only seen in films up to 8-10 nm -much thinner than the particle observed here. The nature of these dislocations could lend insight into the varied morphology of the grown crystallites.…”

Discovering a Cr-Induced Novel Superstructure on Top of a GaN Pseudo “1 × 1” Surface by Scanning Tunneling Microscopy Using a Fe/W Tip

“…It caused the domain boundaries shift one atom row along the “ a ” direction, whereas the boundaries along the “ b ” direction are still roughly continued. The novel structure is either different from the transition metal-induced or reconstructions on the GaN pseudo “1 × 1” surface , or different from the misfit dislocations at the interface of InN/GaN heterostructures . The length of the triangle is around 1.4 nm, and the top and bottom sides of the trapezoid are 1.1 and 2.1 nm.…”

“…The domain boundaries of the triangle and trapezoid form the network lines along the "a" 3 reconstructions on the GaN pseudo "1 × 1" surface 16,26 or different from the misfit dislocations at the interface of InN/GaN heterostructures. 27 The length of the triangle is around 1.4 nm, and the top and bottom sides of the trapezoid are 1.1 and 2.1 nm.…”