TY - JOUR
T1 - Simulation of radial dopant segregation in vertical Bridgman growth of GaSe, a semiconductor with anisotropic solid-phase thermal conductivity
AU - Lee, Hanjie
AU - Pearlstein, Arne J.
N1 - Funding Information:
The authors gratefully acknowledge the comments, suggestions, and information provided by Drs. Nils C. Fernelius and Valeriy G. Voevodin, and an anonymous reviewer. We also very much appreciate the efforts of several people, including Donna Swischer, Irina Bereznaya, Barbara Loomis, Tina Chrzastowski, and Joseph Bentsman to obtain a copy of Ref. [77] , without which this work would not have been possible. The authors gratefully acknowledge support of the Microgravity Science and Applications Division of the National Aeronautics and Space Administration through Grant NAG3-1121 during the early stages of development of the code used herein, and thank the AFRL Window on Science program for sponsoring the visit of Dr. Voevodin. The computations were performed using the facilities of the National Center for Supercomputing Applications.
PY - 2001/9
Y1 - 2001/9
N2 - For a range of growth conditions of practical interest, we simulate liquid- and solid-phase dopant distributions and radial segregation for several dopants (In, Sn, Cu, Se, Zn, and Cd) in vertical Bridgman growth of the nonlinear optical material gallium monoselenide. Besides these dopants, which have been used to modify the properties of Bridgman-grown GaSe and have segregation coefficients in the range 0.01≤k̃≤0.3, we also consider a hypothetical dopant with k̃ = 0.8. The computational model accounts for the anisotropic solid-phase thermal conductivity characteristic of nonlinear optical materials, interface deformation, convection in the melt, and conduction in the ampoule wall. The results show a strong dependence of radial segregation on growth rate over the range 0.25 μm s-1 ≤U≤3 μm s-1, and a much weaker dependence on the maximum ampoule-wall temperature gradient over the range 15°C cm-1 ≤dTb(0)/dz≤60°C cm-1. Overall radial segregation depends weakly on whether the melting temperature is "centered" between the high and low temperatures, and is insensitive to both the 23°C difference in the measured values of the melting temperature, and the large difference between the two measurements of the enthalpy of fusion. The overall radial segregation depends approximately linearly on the product of 1 - k̃ and the growth rate U over the entire range of segregation coefficients and growth rates considered. Radial segregation computed using an isotropic conductivity (one-third the trace of the conductivity tensor) gives results qualitatively different than predictions using the anisotropic conductivity. We also show how localized ampoule-wall heating in the "adiabatic" zone of a three-zone Bridgman furnace can dramatically alter radial segregation by creating one or more additional, weak, toroidal vortices just above the interface.
AB - For a range of growth conditions of practical interest, we simulate liquid- and solid-phase dopant distributions and radial segregation for several dopants (In, Sn, Cu, Se, Zn, and Cd) in vertical Bridgman growth of the nonlinear optical material gallium monoselenide. Besides these dopants, which have been used to modify the properties of Bridgman-grown GaSe and have segregation coefficients in the range 0.01≤k̃≤0.3, we also consider a hypothetical dopant with k̃ = 0.8. The computational model accounts for the anisotropic solid-phase thermal conductivity characteristic of nonlinear optical materials, interface deformation, convection in the melt, and conduction in the ampoule wall. The results show a strong dependence of radial segregation on growth rate over the range 0.25 μm s-1 ≤U≤3 μm s-1, and a much weaker dependence on the maximum ampoule-wall temperature gradient over the range 15°C cm-1 ≤dTb(0)/dz≤60°C cm-1. Overall radial segregation depends weakly on whether the melting temperature is "centered" between the high and low temperatures, and is insensitive to both the 23°C difference in the measured values of the melting temperature, and the large difference between the two measurements of the enthalpy of fusion. The overall radial segregation depends approximately linearly on the product of 1 - k̃ and the growth rate U over the entire range of segregation coefficients and growth rates considered. Radial segregation computed using an isotropic conductivity (one-third the trace of the conductivity tensor) gives results qualitatively different than predictions using the anisotropic conductivity. We also show how localized ampoule-wall heating in the "adiabatic" zone of a three-zone Bridgman furnace can dramatically alter radial segregation by creating one or more additional, weak, toroidal vortices just above the interface.
KW - A1. Computer simulation
KW - A1. Convection
KW - A1. Doping
KW - A1. Segregation
KW - A2. Bridgman technique
KW - B2. Nonlinear optical materials
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U2 - 10.1016/S0022-0248(01)01444-0
DO - 10.1016/S0022-0248(01)01444-0
M3 - Article
AN - SCOPUS:0035452371
SN - 0022-0248
VL - 231
SP - 148
EP - 170
JO - Journal of Crystal Growth
JF - Journal of Crystal Growth
IS - 1-2
ER -