Directions : Each of the next items consists of two statements, one labelled as the `Assertion (A)' and the other as 'Reason (R)' You are to examine these two statements carefully and select the answers to these items using the codes given below :

 Assertion (A): Concentration of acceptor atoms in the region between isolation islands will be much higher p*.than in the p type substrate in an integrated circuit.

Reason (R): This is to prevent the depletion region ' of the reverse-biased isolation to substrate junction from extending into pi" type material. 

In case of reverse bias

p - n Junction Depletion width is given as

\({\rm{W}} = {\rm{\;}}\sqrt {\frac{{2{\rm{E}}}}{{\rm{q}}}\left( {\frac{1}{{{\rm{Na}}}} + \frac{1}{{{\rm{Na}}}}} \right){{\rm{V}}_{\rm{j}}}} \) 

Explanation:

Since the concentration of acceptor atom of p⁺ is higher than P-type substrate and

\(W \propto \frac{1}{{\sqrt {doping} }}\) 

Due to the high concentration of p⁺ substrate in an IC width of the depletion region is less this is because to prevent the depletion region of reverse bias Isolation.

Thus acceptor atom in the region should be high

i.e. N_a should be high

Extra information

Charge in conductivity in Si is more w.r.t. temp.

The most common type of IC is silicon IC due to Si is abundant on earth, and Si is thermally stable

\(\begin{array}{*{20}{c}} {{I_o}\left( {Si} \right)}\\ {nA} \end{array}\begin{array}{*{20}{c}} < \\ {} \end{array}\begin{array}{*{20}{c}} {{I_o}\left( {Ge} \right)}\\ {\mu A} \end{array}\)