
(a)
Interpretation:The mass of dopant required to generate one metric ton n-type silicon semiconductor have to determine.
Concept introduction:In n-type silicon semiconductor, the dopant must contain 5 valence electrons, so that after bonding with silicon (4 electron system) there remains an extra electron. The dopant frequently used for the commercially available silicon semiconductor is phosphorous (P), as the phosphorous impurity in silicon doesn’t increase the weight of the semiconductor much. The bonding pattern and roaming of extra electron of phosphorous generates n-type (negative charged or electron mediated) semiconductor. However, on the amount of dopant the silicon semiconductor may be subdivided into two category: light and heavy semiconductor.
In light silicon semiconductor 1 impurity atom is present per 1,000,000,000 or ppb (parts per billion) silicon atoms. On the other hand for generation of heavy silicon semiconductor 1 atom of impurity needed per 1,000 atom of silicon.
(a)

Answer to Problem 8.105PAE
Solution:The mass of phosphorous required for the doping of silicon for making light and heavy semiconductor are
Explanation of Solution
1 metric ton of silicon =
On conversion of
1 mole of silicon is equivalent to
For making light semiconductor 1 atom of dopant is required per
Henceforth, number of dopant atoms required is
The number of moles of phosphorous required as dopant is
The mass of phosphorous dopant required
Henceforth to make the phosphorous incorporated light semiconductor per metric ton of silicon required
To prepare heavy silicon semiconductor number of dopant atoms required is
The number of moles of phosphorous required as dopant is
The mass of phosphorous dopant required
Henceforth to make the phosphorous incorporated heavy semiconductor per metric ton of silicon required
(b)
Interpretation:The mole fraction of the dopant required to generate commercially available silicon n-type semiconductor.
Concept introduction:The mole number of the impurity or dopant present per unit total mole number of the dopant and substrate in a semiconductor is called the mole fraction of the dopant. It can be expressed as-
(b)

Answer to Problem 8.105PAE
Solution:The mole fraction of dopant phosphorous present in light and heavy 1 metric ton silicon semiconductor are
Explanation of Solution
For light silicon semiconductor doped by phosphorous the mole number of dopant and substrate are
On plugging the values in the equation,
So,
Thus in the light semiconductor the mole fraction of the dopant is
On the other side for heavy semiconductor doped by phosphorous the mole number of dopant and substrate are 35.713 and
On plugging the values in the equation,
So,
Thus in the light semiconductor the mole fraction of the dopant is
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Chapter 8 Solutions
Chemistry for Engineering Students
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