A new acceptor level located 0.111±0.002 eV from the valence band with a peak photoionization cross section of (1.4±0.6) ×10−16 cm2 has been observed in indium-doped silicon. Its presence is revealed both by the low-temperature slope of Hall measurements versus temperature and by the spectral response of the photoconductivity. The concentration of this 0.111-eV level is strongly correlated with the concentration of indium, suggesting that an In complex is responsible for this center.
Strong evidence is presented that the X-level defect, which produces a 0.111-eV acceptor level in Si : In, is a substitional In–substitutional C (Ins-Cs) pair. The concentration of this defect follows a mass-action law with the In and C concentrations, the association constant being (1.4±0.3) ×10−19 cm−3 at 650 °C. Reversible changes in the X-level concentration between anneal temperatures of 650 and 850 °C are observed, and a pair binding energy of 0.7±0.1 eV is estimated. The electronic properties and temperature dependence of the concentration of this center are found to be those expected for a nearest-neighbor Ins-Cs pair.
The breakdown of argon gas containing freon-12 impurity is reported. At high pressure the freon increases the breakdown threshold, while at low pressure it decreases the threshold. This behavior is shown to result from attachment and multiphoton ionization of the freon. The experiment is considered to provide further evidence for multiphoton ionization and for the cascade theory of breakdown.
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