Radial dopant segregation induced by the position of the melt/solid interface in vertical Bridgman-Stockbarger growth system in space
by
Agneta M. Balint
University of the West Timisoara, Department of Physics
Coauthors: Monica Mihailovici (Main author, University of the West Timisoara), Stefan Balint (University of the West Timisoara)

In this paper we make a numerical analysis of the influence of the melt/solid interface position and the length of the melt on the radial dopant segregation for a prototype vertical Bridgman-Stockbarger semiconductor crystal growth system in microgravity.

Computations are made for melt and crystal with thermophysical properties similar to those of gallium-doped germanium ignoring the precrystallization-zone. The melt/solid interface is considered planar and fixed. Calculus reveals, that radial dopant segregation increases, if the melt/solid interface is fixed in the lower half of the adiabatic region, and decreases, if it is fixed in the upper half of the adiabatic region. Reducing the length of the melt leads also to a decrease of radial segregation. The influence of the precrystallization-zone on the radial dopant segregation is also studied. This zone is considered to be a thin layer where we have periodically distributed places which are not available for the dopant. These places can be imagined as some small 'solid inclusions'. Numerical computations made for increasing volumic concentrations of 'solid inclusions' reveal an increase of radial dopant segregation.

For a given volumic concentration of 'solid inclusions', radial segregation decreases by decreasing the length of the melt region.

Date received: January 13, 2000