Defect reactions associated with divacancy elimination in silicon

Defect reactions associated with the elimination of divacancies (V₂) have been studied in n-type Czochralski (Cz) grown and float-zone (FZ) grown Si crystals by means of conventional deep-level transient spectroscopy and high-resolution Laplace deep-level transient spectroscopy (LDLTS). Divacancies were introduced into the crystals by irradiation with 4 MeV electrons. Temperature ranges of the divacancy disappearance were found to be 225-275°C Cz Si crystals and 300-350°C in FZ Si crystals upon 30 min isochronal annealing. Simultaneously with the V₂ disappearance in Cz Si crystals a correlated appearance of two electron traps with activation energies for electron emission 0.23 eV {E(0.23)} and 0.47 eV {E(0.47)} was observed. It is argued that the main mechanism of the V₂ disappearance in Cz Si crystals is related to the interaction of mobile divacancies with interstitial oxygen atoms. This interaction results in the formation of V₂O centres, which are responsible for the E(0.23) and E(0.47) traps. Electronic properties of the V₂O complex were found to be very similar to those of V₂ but energy levels of the two defects could easily be separated using LDLTS. In FZ Si crystals, a few electron traps appeared simultaneously with the V₂ annihillation. The small concentration of these traps compared with the V₂ concentration before annealing prevented their reliable identification.