Segregation and Crystallization Phenomena in Germanium
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SEGREGATION AND CRYSTALLIZATION PHENOMENA IN GERMANIUM
G. J. CLARK IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598 USA A. G. CULLIS Royal Signals and Radar Establishment, St. Andrews Road, Malvern, England D. C. JACOBSON and J. M. POATE Bell Laboratories, 600 Mountain Avenue, Murray Hill, NJ 07974 USA MICHAEL 0. THOMPSON Department of Materials Science, Cornell University, Ithaca, NY 14853
ABSTRACT
While many studies have been made of liquid phase epitaxy impurity trapping and segregation in Si little is known about the equivalent processes in Ge. In this paper we have laser annealed Ge and crystals implanted, at liquid nitrogen temperature, with 200 2 10 Bi ions to doses of 2x 10 5 and 106 ions cm-2 . The samples keV were annealed with Q-switched ruby lasers and an XeC1 excimer laser. We have observed 1) velocity and orientation dependence of the Bi interface instability and cell formation segregation coefficient 2) resulting from constitutional supercooling and 3) amorphization and defect production at high velocities. The phenomena are shown to be analogous to those seen in Si.
INTRODUCTION The energy from pulsed laser irradiation can be used to melt, for a very short time, silicon or germanium crystals to a depth of several thousand angstroms. The melting is followed by non-equilibrium liquid phase, epitaxial regrowth at velocities of up to 20 There has been considerable recent activity] in the use of these experimental mns 1 conditions to study high velocity non-equilibrium crystal growth in Si. Segregation studies have been made on the movement and trapping of implanted impurities in silicon during non-equilibrium crystal growth, the onset of defect-formation during crystal regrowth at high velocities 2 and the amorphization of the Si at extremely high regrowth velocities. Specifically it has been observed that following pulsed ruby laser annealing of Bi and In implanted Si both velocity and orientation dependence are observed in the segregation coefficients up to velocities of - 5 m s- 1 where the segregation coefficients saturate at approximately the same value for both the and the orientations. Equilibrium solid solubilities are exceeded by many orders of magnitude. At high doses (1016 ions cm- 2) cellular microstructure is observed. This occurs when there is constituMat. Res.
Soc. Symp. Proc. Vol. 13 (1983) OElsevier Science Publishing Co.,
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tional supercooling in the resolidifying liquid so that the liquid-solid interface becomes unstable and breaks down. At velocities greater then - 5 m s- 1 defects in the form of twins are observed for the orientation but not for the . At extremely high velocities (> 15 m s- 1) amorphous Si is produced. In this paper, we measure for the first time such segregation and recrystallization phenomena in Ge with the aim of determining the parallel between Si and Ge in this regime of ultra-rapid crystal growth. Specifically we have investigated segregation and crystallization of Bi implanted and < 111> Ge with regrowth velocities in the range
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