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Another of our activities deals with the fabrication and study
of stacks with high-mobility channel, using alternative semiconductors
(germanium, gallium arsenide, etc.) to silicon. In this case the
device performance is improved due to the higher carrier velocity,
which allows more electrical current for the same electric field.
The potential applications are in high-speed digital electronics
and integrated optoelectronics.
The ultimate goal is to fabricate germanium- and compound-semiconductor-on-insulator
(GOI, CSOI) stacks. The followed procedure is to deposit a graded
epitaxial oxide on a silicon substrate, followed by a thin film
of Ge or GaAs, on which a suitable high-κ dielectrics layer
is grown. This sequence of layers grown by molecular beam epitaxy
(MBE) is then applied in the fabrication of field effect transistors.
For this purpose the appropriate materials are combined in order
to achieve the best tradeoff between high mobility and small lattice
mismatch.
Part of this work is done in the framework of the EU-funded project
ET4US (Epitaxial Technologies for Ultimate Scaling) involving several
partners. For the growth of the new materials, a new MBE cluster
for 200 mm wafer has been installed.
References
| [1] |
Demonstration of electron and hole inversion
inversion in GaAs MOS capacitors with HfO2 gate dielectrics
and amorphous Si/SiO2 interlayers,
S. J. Koester, E. W. Kiewra, Yanning Sun, D. A. Neumayer, J.
A. Ott, M. Copel,
D. K. Sadana, D. J. Webb, J. Fompeyrine, J.-P. Locquet, C. Marchiori,
M. Sousa and R. Germann,
Appl. Phys. Lett., 89, 042104 1-3 (2006). |
| [2] |
HfO2 high-k dielectrics grown on Ge(100) with
ultrathin passivation layers: a TEM study
J. W. Seo, Ch. Dieker, J.-P. Locquet, G. Mavrou and A. Dimoulas,
Appl. Phys. Lett., 87, 221906 1-3 (2005). |
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Drift velocity versus electric field for different
semiconductors. The red arrows show how drift velocity, i.e.,
mobility, can be improved at even lower electric fields by replacing
silicon by other high-mobility semiconductors. |
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View of the atomic lattice of a perovskite oxide
film ABO3 sandwiched between two semiconductors such as Si and
Ge. |
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Lattice parameters of various perovskites ABO3
with the different A and B cations compared to the lattice parameters
of alternative semiconductors to Si and their respective mobilities.
The right choice of perovskite and semiconductor pair will have
a good lattice match and a high carrier mobility in the semiconductor. |
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Three stages of the ET4US European project, which
started in 2004. |
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