13.3.2019

Roman Gröger (Ústav fyziky materiálů AVČR Brno):
Extended defects in epitaxial films of wurtzite III-nitrides


Abstrakt:

The physical properties of heteroepitaxial films of wurtzite III-nitrides are
strongly affected by threading dislocations, which are expected to nucleate due
to large mismatch of the lattice parameters of the film and the substrate
(typically sapphire or Si). These defects are known to reduce the electron
mobility and to generate deep defect states in the bandgap through which they
affect the electrical and optoelectronic properties of the device. In this talk,
we provide an overview of the mechanisms that may be responsible for the
nucleation of these defects at low and high temperatures. A simple theoretical
model will be presented that may  explain the discrepancy in relative densities
of the three dislocation types predicted by linear elasticity and observed in
TEM using the weak-beam dark-field method. The changes of surface topography of
AlN {0001} film grown on Si {111} by MOCVD will be described using AFM and
correlated with the electron beam induced current (EBIC) generated by 5 keV
electron beam in SEM. These studies provide the size of the "fingerprint" of
individual defects in the EBIC signal and thus a measure of their recombination
efficiencies.