Electrically active defects induced by electron irradiation in Czochralski (Cz)grown Si crystals with low carbon content (N C 2 × 10 15 cm −3 ) have been studied by means of Hall effect measurements, deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS (LDLTS). It has been found that in n-type carbon-lean Cz-Si irradiated at room temperature a centre with an acceptor level at E c − 0.11 eV (E 0.11 ) is one of the dominant radiation-induced defects. This centre is not observed after irradiation in Cz-Si crystals with N C > 10 16 cm −3 . The E 0.11 trap anneals out in the temperature range 100-130 • C with the activation energy 1.35 eV.In p-type Cz-Si crystals with low carbon content and boron (N B 2 × 10 14 cm −3 ) one of the dominant radiation-induced defects has been found to be a bistable centre with an energy level at E v +0.255 eV (H 0.255 ). It has been inferred from the analysis of temperature dependences of electron occupancy of this level that it is the E(0/++) level of a defect with negative Hubbard correlation energy (negative U ). The activation energy for hole emission from the doubly positively charged state of the H 0.255 centre has been determined as 0.358 eV from LDLTS measurements.It is argued that the E 0.11 and H 0.255 energy levels are related to a complex incorporating an oxygen dimer and Si self-interstitial.
The electronic properties and structure of a complex incorporating a self-interstitial (I) and two oxygen atoms are presented by a combination of deep level transient spectroscopy (DLTS), infrared absorption spectroscopy and ab-initio modeling studies. It is argued that the IO2 complex in Si can exist in four charge states (IO− 2 , IO02 , IO+ 2 , and IO++ 2 ). The first and the second donor levels of the IO2 complex show an inverted location order in the gap, leading to a E(0/ + +) occupancy level at Ev + 0.255 eV. Activation energies for hole emission, transformation barriers between different structures, and positions of LVM lines for different configurations and charge states have been determined. These observables were calculated by density-functional calculations, which show that they are accounted for if we consider at least two charge-dependent defect structures.
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