Abstract
Point defects in semiconductors play an important role in governing the material's electronic properties.
Intrinsic point defects consist of the displaced atoms of the lattice itself and in general form deep levels that act as
trapping centers for conduction electrons or holes.
Non-paramagnetic intrinsic centers in low concentrations are best accessible to investigation by radioactive probe atoms placed
in the atomic neighbourhood of the defect.
The decay of a radioactive atom, substitutionally incorporated into the lattice of the semiconductor, can produce
a single isolated Frenkel-pair, if the recoil energy induced by the neutrino-emission accompanying the decay exceeds a certain
threshold energy.
The neutrino-recoil-method is used to investigate the formation of intrinsic point defects in the two compound
semiconductors InSb (n-type) and CdTe (p-type).
Radioactive Te is implanted into InSb via a proton-induced reaction, into CdTe via a heavy-ion reaction.
The subsequent decay of Te to Sb transfers a recoil energy of 12eV to the atom, an amount that lies just above the threshold energies in
both semiconductors as they have been obtained through electron-irradiation experiments.
The following decay leads to 119Sn that is used as a probe atom for Mößbauer-spectroscopy.
The analysis and interpretation of the experimental results require the consideration of all available measurement parameters,
namely the hyperfine parameters isomer shift and quadrupole splitting as well as the line intensity as a time-dependent parameter.
The results obtained in the two materials differ from each other fundamentally.
InSb displays three different types of intrinsic point defects created by the neutrino recoil process, i.e.
an interstitial site and a site on each of its sublattices with an adjacent vacancy, whereas CdTe shows only one, which is
accompanied by an unexpectedly large field gradient.
In addition, the substitutional site in CdTe induces a significant distortion of its local surrounding, that can be interpreted to be due
to a Jahn-Teller-effect.
Furthermore, within CdTe Sb attracts intrinsic oxygen when being anneald at temperatures well above 600°C, a process
that exhibits itself in the formation of SnO2-complexes.
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