The
search for new wide-band-gap materials is intensifying to satisfy
the need for more advanced and energy-efficient power electronic devices.
Ga2O3 has emerged as an alternative to SiC and
GaN, sparking a renewed interest in its fundamental properties beyond
the main β-phase. Here, three polymorphs of Ga2O3, α, β, and ε, are investigated using X-ray
diffraction, X-ray photoelectron and absorption spectroscopy, and ab initio theoretical approaches to gain insights into their
structure–electronic structure relationships. Valence and conduction
electronic structure as well as semicore and core states are probed,
providing a complete picture of the influence of local coordination
environments on the electronic structure. State-of-the-art electronic
structure theory, including all-electron density functional theory
and many-body perturbation theory, provides detailed understanding
of the spectroscopic results. The calculated spectra provide very
accurate descriptions of all experimental spectra and additionally
illuminate the origin of observed spectral features. This work provides
a strong basis for the exploration of the Ga2O3 polymorphs as materials at the heart of future electronic device
generations.
We
report on the microscopic behavior of residual hydrogen on nanometric
field emitters. By using homogeneous or heterostructured semiconductor
specimens analyzed in a laser-assisted atom probe, it is possible
to study how the relative abundances of the ionic species H+, H2
+, and H3
+ depend
on the microscopic electric field, estimated through post-ionization
statistics. In the case of Ga-containing semiconductors, the relative
abundances of H+, H2
+, and H3
+ follow a common trend, independent of the nonmetallic
component of the matrix. The dependence of the total H flux on the
electric field exhibits a more complex behavior, which depends also
on the spatial direction of the variation of the field (in-depth or
on-surface). The analysis of multiple detection events provides further
insights into surface chemistry. Noticeably, H+–H3
+ ion pairs are both correlated in number and separated
by very small distances on the detector space, suggesting a possible
reaction 2H2 → H3
++H++2e– taking place on the field emitter surface.
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