Department of Materials Science and Engineering
Learn more about
|Professor, V. Chair;
BSc in Physics: Purdue University in 1981; MSc (1983) and PhD (1986)
in Electrical Engineering: University of California, Los
Research interest: increased
functionality in Si-based materials and devices. There are three projects
currently being pursued:
RF Cross-talk Isolation:
Portable electronics, especially the IC’s for cellular telephone
handsets, is the fastest growing sector of the entire microelectronics
industry. The rapid expansion of the market is fueled by the reduction in
cost, which in turn is made possible by the increasing scale of
integration. The key components of today’s cellular telephone handset
consist of digital and RF analog circuits, and they are on separate chips.
Further integration of the digital and RF analog circuits is hampered by
the cross-talk issue, for which there is no viable solution at the current
Our effort concentrates on the reduction of the
cross-talk using porous Si. We make use of the high resistivity
characteristics of porous Si for isolation. The porous Si formation
process converts the material with resisitivity as low as 0.005 W-cm in
the bulk form to as high as 1 MW-cm in the porous form. Our objectives are
to understand the various properties such as the mechanical strength, the
impedance of the porous Si structure, the details of vapor phase
deposition process involving porous structures, and to develop this into a
Si VLSI compatible process module.
Self-assembled Quantum Dot Arrays
by epitaxy: Along with the continued shrinking of device dimensions in
Si VLSI, the task of exploring and understanding new device structures
that are based on quantum mechanical effects has become more urgent. These
are devices with their critical dimensions smaller than the quantum
mechanical wavelength of electrons. One such group of devices is based on
semiconductor islands of several hundred angstroms in size that are formed
during hetero-epitaxial growths, also known as self-organized quantum
dots. One of the major challenges in fabricating self-organized quantum
dots is the uniformity in the size and the spatial distribution. Under
current practice, semiconductor islands form at random. Consequently, they
are randomly distributed with a size distribution that is wider than
desirable for various device applications.
The objective of our research is to fabricate
three-dimensional semiconductor quantum dot arrays with uniform spatial
and size distribution. It is well known that for multi-layer
self-organized island structures, the islands in the upper layer sense the
strain field of the underlying islands. As a result, islands in subsequent
layers naturally line up with the islands underneath. The task of
fabricating a three-dimensional regular array is thus reduced to that of a
two-dimensional regular array. Our approach is to pattern the substrate
using three different, non-lithographic, methods. The first method
utilizes the periodic strain field of a buried misfit dislocation network.
The second method relies on the periodic strain field of a compliant
substrate. The third method uses what is known as “nature lithography”.
The epitaxy growth is done with molecular beam epitaxy.
Si Optical Bench:
Si optical bench refers to the class of photonic devices consists of SiO2 waveguides fabricated on Si
substrates. These devices are used in switches and as transceivers in the
optical communication network. Our research efforts focus on two aspects
of the technological challenges: developing a more efficient method of
fabricating thick (>15 mm) SiO2
cladding layers, and reducing the stress in the SiO2 waveguides which causes
- “An Approach For Fabricating High
Performance Inductors On Low Resistivity Substate”, Y.H. Xie, M.R.
Frei, A.J. Becker, C.A. King, D. Kossives, L.T. Gomez, and S.K. Theiss,
IEEE Journ. Solid State Circuits, 33, 1433 (1998);
- “ Experimental Evidence for a
two-dimensional quantized Hall insulator”, M. Hilke, D.Shahar,
S.H.Song, D.C.Tsui, Y.H.Xie, and Don Monroe, Nature, 395, 675
- “Relaxed Template for Fabricating
Regularly Distributed Quantum Dot Arrays”, Y.H.Xie, S.B.Samavedam,
M. Bulsara, T.A.Langdo, and E.A.Fitzgerald, Appl. Phys. Lett., 71,
- "Semiconductor Surface
Roughness: Dependence on Sign and Magnitude of Bulk
Strain", Y.H. Xie, G.H. Gilmer, C. Roland, P.J. Silverman, S.K.
Buratto, J.Y. Cheng, E.A. Fitzgerald, A.R. Kortan, S. Schuppler, M.A.
Marcus, P.H. Citrin, Phys. Rev. Lett., 73, 3006
- "Very High Mobility
Two-Dimensional Hole Gas in Si/GexSi1-x/Ge Structures Grown by
Molecular Beam Epitaxy," Y.-H. Xie, D.P. Monroe, E.A. Fitzgerald,
P.J. Silverman, F.A. Thiel, G.P. Watson, Appl. Phys. Lett., 63(16),
- "Fabrication of High Mobility
Two-Dimensional Electron and Hole Gases," Y.-H. Xie, E.A.
Fitzgerald, D.P. Monroe, P.J. Silverman, G.P.Watson, J.
Appl. Phys., 73(12), 8364 (1993);
- "Extremely High Electron Mobility
in Si/Gex Si1-x Structures Grown by Molecular Beam Epitaxy", Y.J.
Mii, Y.-H. Xie, E. A. Fitzgerald, D. Monroe, F. A. Thiel, B. E. Weir,
and L. C. Feldman, Appl. Phys. Lett., 59, 1611 (1991).
- "Absorption and Luminescence
Studies of Free-standing Porous Silicon Films," Y.H. Xie, M.S.
Hybertsen, W.L. Wilson, S.A. Ipri, G.E. Carver, W.L. Brown, E. Dons,
B.E. Weir, A.R. Kortan, G.P. Watson, and A.J. Liddle, Phys. Rev.
B, 49(8), 5386 (1994);
- "Light Emission From
Silicon", S.S. Iyer, Y.-H. Xie, Science, 260, 40