TEM investigation of anisotropic defect structure in cubic GaN/AlGaAs/GaAs(001) grown by MOVPE

Abstract

The effects of AlxGa1‐xAs buffer layer insertion on the defect structures and their distribution in cubic (c‐) GaN films on GaAs (001) substrates grown by low‐pressure metalorganic vapor phase epitaxy have been investigated by means of bright‐ and dark‐field cross‐sectional transmission electron microscopy. It is demonstrated that a 300‐nm‐thick Al0.2Ga0.8As buffer layer can protect the GaAs (001) surface from thermal decomposition during the growth at 960 °C, remaining a growth of c‐GaN on GaAs substrate without any voids at the interface. Two different types of defect structures having an anisotropic distribution between the [110] and [1‐10] zone axes were observed. For the [110] zone‐axis, the pyramid‐shaped grains, which are proposed to construct from planar defects, such as SFs and twins, were observed. On the other hand, for the [1‐10] zone‐axis, a dense cubic phase structure with less contribution of planar defects was observed. However, threading dislocations, which were produced by a coalescence of pyramid‐shaped grains in the [110] direction, were observed at the top regions of c‐GaN layer. Both types of defect structures have an anisotropic distribution within a cubic symmetry that may be due to different atomic structures on the AlGaAs surface along the [110] and [1‐10] crystallographic directions. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

TEM Analysis of Structural Phase Transition in MBE Grown Cubic InN on MgO (001) by MBE: Effect of Hexagonal Phase Inclusion in an C-Gan Nucleation Layer

“…Bright contrast lines represent a generation of hexagonal phase in form of planar defects in c-InN layer, which generated from the interface between c-InN /c-GaN. It is known that c-GaN suffer from an existing of SFs, which is associated to a formation of hexagonal phase on the cubic {111} facets [12,13]. There are parts of planar defects in c-GaN nucleation layer propagated to the c-InN/c-GaN interface, which are elongated continually to the c-InN layer as indicated by yellow arrows.…”

Cubic zincblende gallium nitride for green-wavelength light-emitting diodes

“…With a low formation energy in fcc crystals [55], it is questionable whether stacking faults help to relieve strain. Twinning has been reported for zincblende GaN grown on GaAs [50,54,56]; however, the mechanism by which strain is relieved is not clear.…”