Oxygen '96
Early Stages of Oxygen Precipitation in Silicon
INFLUENCE OF ISOVALENT DOPING ON THE PROCESSES OF THERMAL
DONORS FORMATION IN SILICON
L. Khirunenko,
V. Shakhovtsov
V. Shumov and
V. Yashnik
Institute of Physics of the National Academy of Sciences of Ukraine
252650, Kiev-22, Pr.Nauki 46, Ukraine
Key words: oxygen, silicon, germanium, thermal donors
It is known the efficiency of oxygen-related thermal donors (TD)
formation in silicon depends on its impurity composition. Especially
it is concerned isovalent impurities such as C and Ge. In this
work the investigation of influence of doping with germanium on the
processes of low temperatures (450 degrees C) thermodonors formation
in Si are presented. The concentration of Ge in Si was altered from
3x1018 to 2x1020 cm-3. The
measurements were made using IR Fourier spectroscopy.
We have
observed appearance of new additional TD absorption lines and also
complex structure of individual bands at the concentration of Ge more
than 5x1018 cm-3 in Si. The energy position of
these lines is very close to that for lines observing in specially
undoped Si. Using illumination the components connected with
transitions from exited states were distinguished. Three groups of
lines connected with new TD types in Si were identified using the
calculations in the effective mass theory approximation.
Investigations of differential spectra have shown that as
concentration of Ge increases the efficiency of formation of TD
typical for specially undoped Si gradually is decreased. At the same
time the efficiency of introduction new TD is much lower in Si
than that in Si. As a result, beginning from concentration of Ge
1019 cm-3 increasing of thermal stability of Si
is observed. At the concentration of Ge about 1020
cm-3 the total concentration of TD decreases more than an
order of magnitude. It was shown that effect of decreasing of TD
formation takes place also for "shallow" thermodonors
(EI=0.036 eV) which appear at the initial heat treatment
stage (1-5 hours).
Observed effects are explained by formation a
new type origin of TD centres in Si at doping with Ge arising as a
consequence of correlated distribution of atoms Ge and Si.
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