A MOS capacitor has a metal gate and p-type silicon substrate at 300 K. Its inversion carrier sheet density is 21011\ cm-2 at V G=0.8 V and 41011\ cm-2 at V G=1.3 V. What is the density at V G=1.8 V?

$4.5\times10^{11}\ \mathrm{cm^{-2}}$

$7.2\times10^{11}\ \mathrm{cm^{-2}}$

$8.4\times10^{11}\ \mathrm{cm^{-2}}$

GATE 2016 EC (EC2) – Question 45

Electronic Devices · P-N Junction and Semiconductor Devices · 2 marks · Multiple choice

A MOS capacitor has a metal gate and p-type silicon substrate at 300 K. Its inversion carrier sheet density is $2\times10^{11}\ \mathrm{cm^{-2}}$ at $V_G=0.8$ V and $4\times10^{11}\ \mathrm{cm^{-2}}$ at $V_G=1.3$ V. What is the density at $V_G=1.8$ V?

$4.5\times10^{11}\ \mathrm{cm^{-2}}$
$6.0\times10^{11}\ \mathrm{cm^{-2}}$
$7.2\times10^{11}\ \mathrm{cm^{-2}}$
$8.4\times10^{11}\ \mathrm{cm^{-2}}$

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Correct answer: (B) $6.0\times10^{11}\ \mathrm{cm^{-2}}$

Explanation

In strong inversion, incremental gate voltage predominantly increases inversion charge, giving a linear relation between sheet density and gate overdrive.

The given 0.5 V increase raises density by $2\times10^{11}\ \mathrm{cm^{-2}}$. The next equal 0.5 V increase raises it by the same amount. Therefore the density is **$6.0\times10^{11}\ \mathrm{cm^{-2}}$, B**.

GATE 2016 EC (EC2) – Question 45

Explanation

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