Ge-Si AHP
Abstract
This research project will focus on the understanding of melt
growth characteristics of
germanium-silicon
(Ge-Si) alloy crystals, which are
promising candidates in thermopower
generation, photovoltaics, cell
phones, handsets, GPS systems, collision warning systems, and
data converters.
Melt
growth allows large-scale production of semiconductor crystals.
However, growth of Ge-Si single
crystals from melt is extremely sensitive to experimental
parameters. Obtaining accurate thermal data near the
solid/liquid (s/l) interface and so knowing the fluid flow
characteristics during Ge-Si alloy
crystals are essential to control the growth, which is not easy
with conventional techniques. Especially, because of widely
varying segregation coefficient, large density differences, and
large solidification range in the case of
Ge-Si growth, it is important to keep the interface
planar at a constant temperature to avoid compositional
fluctuations that may lead to interface instability and
degradation of single crystallinity.
An
innovative approach (Axial Heat Processing -AHP-) will be used
in this study. The AHP technique will permit close control of
convective effects and thermal field near the growth interface.
AHP achieves these by using a heater immersed in melt near s/l
interface. Power and position of the heater can be controlled as
desired to promote planar interface and laminar fluid flow. Such
parameters as the fluid flow, concentration fields in the melt
and solid, and interface shape, position, and temperature will
be assessed. All these growth parameters then will be correlated
to interface stability, namely the transition from single to
cellular or dendritic growth.
As
Ge-Si alloys find use in
microelectronics in different industries, high quality
Ge-Si alloy single crystals can
especially serve Turkey’s space program as they can be used in
applications to convert waste exhaust heat and solar power to
useful energy that is needed in deep space exploration vehicles
as well as in applications on earth such as those mentioned in
the opening paragraph. This research may also initiate new
industrial fields in Turkey, hence resulting in new employment
opportunities.
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