Thin films of stoichiometric cubic TiN for ohmic contact formation are dire
ctly deposited, by rf magnetron sputtering at room temperature, on (0001) s
urfaces of GaN epilayers grown on c-plane sapphire, Chemical etching and in
situ dry etching of the free GaN surface allows an epitaxial growth of the
deposited TiN films as revealed by high resolution electron microscopy obs
ervations. Taking into account the experimentally determined orientation re
lationship of the two structures, (0001) GaN parallel to (111) TiN, [1(1) o
ver bar 20] GaN parallel to [1(1) over bar 0] TiN, families of dislocations
are expected in the interface plane to accommodate the misfit (similar to5
.8%) with a spacing of 4.5 nm. The mathematical formulation of the circuit
mapping technique is used to analyse the misfit dislocation content on HREM
images since it allows the exact determination of the Burgers vector. This
gives 1/2[0(0)over bar 1>] TiN or 1/3[1(2) over bar 10] GaN. A demistep of
height c(GaN)/2 is observed at the TiN/GaN interface interface and from th
ere a (1(1) over bar 2) twin emanates into the TiN layer. It appears that s
uch demisteps have an important role in mediating the columnar growth of th
e TiN material.