Luminescence studies of transition metal related defects in crystalline silicon
McGuigan, Kevin Gerard (1989) Luminescence studies of transition metal related defects in crystalline silicon. PhD thesis, Dublin City University.
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Infra-red photoluminescence (PL) spectra of zinc and copper
related defects in silicon are presented in this thesis.
Seven new PL systems with principal zero phonon lines
at 919.8, 943.67, 945.8, 1033.5, 1059.9, 1090.7 and 1129.8
meV are discussed. All of the spectra can be classified as
being due to isoelectronic bound exciton ( IBE )
recombination. Although the identities of the binding centres
have not been conclusively established clear evidence has
been obtained in most cases for the involvement of at least
one specific transition metal ( TM ) impurity element.
The PL systems at 945.8, 919.8 and 1059.9 meV are all
observed in silicon diffused with zinc and another TM. The
945.8 meV system is observed in silicon diffused with zinc at
1100° C for 16 hours. The system is not created by
interstitial Mn and substitutional Zn as previously
suggested. The 919 meV system is observed in silicon
co-diffused with zinc and copper at 1100° C for 16 hours,
while the 1059.9 meV system is most clearly observed in
SisFeZn quenched from 1000° C.
For silicon implanted with zinc the 1129.8 and 1090.7 meV
systems are observed. Both of these systems have ground state
and excited state splittings placing them in a minority group
of IBE centres in silicon associated with deep acceptors and
including the indium and thallium systems.
The quenching rate is found to be crucial for samples
diffused with copper only. Slow quenches produce the 1034 meV
SK system. Zeeman studies on the zero phonon lines of this
centre reveal a singlet - triplet nature indicative of a
strong central cell potential about the defect as well as a
strong crystal field reaction. Rapid quenches combined with
low copper concentrations produces the 943.7 Cu PL system.
Uniaxial stress and magnetic field measurements on this
centre suggest that the two lowest energy transitions arise
from bound exciton recombination at a defect with tetrahedral
or near tetrahedral symmetry. Diffusion rate calculations
show that a single interstitial copper atom is not the most
likely configuration . A larger defect involving one or more atoms in a Td arrangement is more likely, perhaps similar to
to those already reported for the Mn4 and Li^ defects in PL
and for the NL22 Fe related centre in EPR.
It is concluded that diffusion is not a suitable method of
introducing transition metal impurities into silicon since
the process is extremely susceptible to contamination.
Implantation of the desired element followed by rapid thermal
annealing is suggested as a much more promising avenue of
investigation since this method affords much more control
over the concentration, implantation depth and most
importantly of all, the identity of the chemical element
introduced into the host crystal.
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