Determination of flow pattern defect area by μ-photoconductivity decay lifetime measurement

Flow pattern defects (FPDs), the decrease in interstitial oxygen concentration during heat treatment and lr-photoconductivity decay (mu-PCD) lifetime were measured precisely in the radial direction using samples with different grown-in defect densities and defect generation areas. In the inner and/or outer region adjacent to the rim of the FPD area where FPD density was zero, a peak and/or a valley of mu-PCD lifetime distribution were observed. It was found that the mu-PCD lifetime distribution depended on the behavior of oxygen precipitation, especially on anomalous oxygen precipitation (AOP). In the case of FPD area larger than about 175 mm in diameter, the edge effect became dominant and it was difficult to observe a peak or a valley in the mu-PCD lifetime distribution due to AOP. The FPD area, however, could be monitored by the mu-PCD lifetime measurement. The relationship between mu-PCD lifetime and oxygen precipitation rate was also interpreted.