Defects induced by doping

Several other experiments confirm the high defect density in doped 

The variation of the defect density with doping level, as measured by the different experiments, is shown for phosphorus doping in Fig. 5.9. The defect density increases with the square root of the phosphorus concentration. 

The same relation applies for the dopants boron and arsenic and, indeed, the total defect density is approximately the same for all three dopants. The dopant concentration in Fig. 5.9 is that of the gas phase impurity concentration, C, not that of the solid. The equivalent plot against C, is changed only slightly for boron and phosphorus, but the arsenic data are substantially different, because of the large and nonlinear distribution coefficient shown in Fig. 5.4. A challenge for any model of doping is to explain both the square root dependence of the defect density and why this applies to the gas concentrations and not to those of the grown film. 

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