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QPages 419-421: Q12: HC Verma: Concepts of Physics - Volume 2 Semiconductors and Semiconductor Devices Pages 419-421: Q12 Solution: Estimate the proportion of boron impurity which will increase…

Estimate the proportion of boron impurity which will increase the conductivity of a pure silicon sample by a factor of 100. Assume that each boron atom creates a hole and the concentration of holes in pure silicon at the same temperature is 7×10157 \times 10^{15} holes per cubic metre. Density of silicon 5×10285 \times 10^{28} atoms per cubic metre.

Step-by-Step Verified Solution

**Answer:** Proportion of boron impurity � 2 _ 10___. **Step-by-Step Explanation:** Given: Pure silicon hole concentration = 7 _ 10__ per m_. Conductivity increased by factor 100. Required hole concentration = 100 _ 7 _ 10__ = 7 _ 10__ per m_. Extra holes needed = 7 _ 10__ - 7 _ 10__ � 7 _ 10__ per m_. Density of silicon = 5 _ 10__ atoms/m_. Proportion = (7 _ 10__)/(5 _ 10__) = 1.4 _ 10___ .

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