Abstract
The goal of this thesis is to study the effect of residual gravity on crystal growth of Silicon Germanium GE0.98 Si0.02 using the Traveling Heater Method (THM). This method has proven to be one of the most efficient techniques to grow high-quality crystals because it can be grown at relatively low temperatures compared to existing crystal growth techniques. Yet, because of natural convection due to earth's gravity, imperfection in terms of silicon distribution along the growth interface occurs. By growing crystals in a space environment, residual gravity represented by a static microgravity component and a sinusoidal component would decrease the intensity of the convective flow, which in return would lead to a more uniform silicon distribution. However, g-jitter fluctuation has proven to have a noticeable effect on the silicon distribution. Therefore, as an initial step to understand the behavior of crystal growth in space, each component of the g-jitter force will be studied thoroughly. The momentum, mass and energy equations, representing the 3D TSM model, were solved using finite element means. The preliminary results indicate that the complexity and the intensity of the silicon distribution along the growth interface are proportional to the convective flow, that partially controls the migration of silicon. Therefore, the quality of the crystal growth is assessed based on the behavior of the flow along the solvent regime. Based on the imposed static gravity in the range of 10-6 go to 10-3 go, the flow was determined to be in a diffusion mode with a velocity ranging from 10-6 cm/sec to 10-3 cm/sec. As a matter of fact, the flow intensity was noted to be positively proportional to the dominant component of both the static and the amplitude of the imposed g-jitter and negatively proportional to the frequency of the sinusoidal g-jitter. Consequently, realistic space growth conditions have proven to be an effective way of producing a homogeneous crystal since a flawless crystal silicon distribution is obtained at the growth interface.
Highlights
Semiconductors are special materials that conduct differently under different conditions, having conductivities intermediate to those of conductors like copper and insulators likewood or plastic
The results have proven that the reduction of gravity has a beneficial influence on the quality of crystal growth
The results showed that the g-jitter frequency and temperature gradients both contribute to the effect of convective flow
Summary
Gravitational Amplitude (CmlS2) Non-dimensionalized gravitational amplitude Non-dimensionalized concentration (atomic %) Solute concentration (atomic %) Reference solute concentration (atomic %) Change in concentration (atomic %) Specific heat capacity at constant pressure (cal/g.K) Reference diameter (cm) Axial unit vector Sinusoidal Frequency Electric field (volt/cm) Grashof number Gravity (cm/S2) Earth gravity (cm/s2) Non-dimensionalized gravity Hartmann number Latent heat (cal/g) Pressure (g/cm2.s2) Prandtl number Radial direction(cm) Reynolds number Non-dimensionalized radial direction Schmidt number Temperature eC).
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