Title
2D electrons in epitaxial strained Germanium quantum wells
Description
Carrier mobility determines how fast a carrier, i.e. electron or hole, can move in a solid
material under applied electric field. It is one of the most important material’s parameter,
determining its suitability for an application in electronic devices. High mobility and the existence
of a reasonably large energy band gap makes any semiconductor material attractive and suitable
for applications in large variety of electronic devices including Metal Oxide Semiconductor Field
Effect Transistor (MOSFET). This is a core device present in modern Silicon (Si) based
Complementary Metal Oxide Semiconductor (CMOS) technology used in the fabrication of
Central Processor Units (CPUs), memory and many other devices incorporated in computers and
portable electronic devices. Si is one of the most important materials in modern semiconductor
technology. However, in order to maintain existing industrial trend in improving performance of
continuously scaling down to sub 10 nm FET devices, new materials or device architectures have
to be introduced. Germanium (Ge) is a semiconductor material which has high intrinsic 3D hole
and electron mobilities among other known semiconductor materials. In particular, its hole
mobility is the highest among existing semiconductors. Biaxial compressive strain further
enhances the hole mobility in Ge. In practice, this is obtained by epitaxial growth of a
compressively strained Ge epilayer, a few nanometers thick, on an underlying standard Si substrate
via an intermediate strain-relaxed SiGe buffer. The strain narrows the band gap of Ge and causes
the appearance of a QW in the valence band. Holes confined in the strained Ge QW form a twodimensional hole gas (2DHG) and have an increased mobility due both to their lower effective
mass and reduced scattering factors in this material system. These hole mobilities are the highest
not only among the group-IV Si and Ge based semiconductors, but also among p-type III-V and
II-VI materials. However, existence of 2D Electron Gas in strained Ge QWs has not been
demonstrated so far.
This is a unique opportunity to undertake a project at the cutting edge of applied physics and
materials science. You will be involved in realization of the 2DEG in strained Ge QWs and
research of their basic transport properties (mobility, effective mass, etc). The novel structures
will be created by epitaxial growth by an industrial type Chemical Vapour Deposition (CVD) of
Ge QW heterostructures on underlying Si substrates. A number of characterization techniques and
experimental setups will be used to research electrical, magnetotransport, structural and optical
properties of novel materials. The future success of the strained Ge QW heterostructures depends
on our ability to understand their transport phenomena and other material properties. Successful
outcome from the project would lead to high impact publications in international scientific journals
and application of developed materials in a variety of electronic and spintronic devices using
capabilities of our academic and industrial collaborators.
This PhD studentship is available for an immediate start. To discuss this project further contact:
Dr Maksym Myronov (M.Myronov@warwick.ac.uk)