Valence band density of states of zinc-blende and wurtzite InN from x-ray photoemission spectroscopy and first-principles calculations

The valence band density of states (VB-DOS) of zinc-blende InN(001) is investigated using a combination of high-resolution x-ray photoemission spectroscopy and quasiparticle corrected density functional theory. The zinc-blende VB-DOS can be characterized by three main regions: a plateau region after the initial rise in the DOS, followed by a shoulder on this region and a second narrow but intense peak, similar to other III-V and II-VI semiconductor compounds. Good general agreement was observed between the experimental and theoretical results. Tentative evidence for an
s
−
d
coupling due to the interaction between valence-like
N
2
s
states and semicore-like
In
4
d
states is also identified. Measurements and calculations for wurtzite
In
N
(
11
¯
2
0
)
are shown to yield a VB-DOS similar to that of zinc-blende InN, although the nonzero crystal field and different Brillouin zone shape in this case lead to a more complicated band structure which modifies the DOS. In adlayers terminating the
In
N
(
11
¯
2
0
)
surface are also evident in the experimental VB-DOS, and these are discussed.