K. Lawniczak-jablonska et al., Electronic states in valence and conduction bands of group-III nitrides: Experiment and theory, PHYS REV B, 61(24), 2000, pp. 16623-16632
A comprehensive study of the electronic structure of group-III nitrides (Al
N, GaN, InN, and BN) crystallizing in the wurtzite, zinc-blende, and graphi
telike hexagonal (BN) structures is presented. A large set of the x-ray emi
ssion and absorption spectra was collected at the several synchrotron radia
tion facilities at installations offering the highest possible energy resol
ution. By taking advantage of the linear polarization of the synchrotron ra
diation and making careful crystallographic orientation of the samples, the
bonds along c axis (pi) and "in plane'' (sigma) in the wurtzite structure
could be separately examined. Particularly for AlN we found pronounced anis
otropy of the studied bonds. The experimental spectra are compared directly
with ab initio calculations of the partial density of states projected on
the cation and anion atomic sites. For the GaN, AlN, and InN the agreement
between structures observed in the calculated density of states (DOS) and s
tructures observed in the experimental spectra is very good. In the case of
hexagonal BN we have found an important influence of insufficient core scr
eening in the x-ray spectra that influences the DOS distribution. The ionic
ity of the considered nitrides is also discussed.