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The junction on a step-graded p-n junction diode is doped with NA corresponding to 1 acceptor atom per 106 Si atoms. The contact potential V0?
(Assume NA = ND, ni = 1·45 × 1010/ cm3 and Si has 5 × 1028 atoms/m3)
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- 751·8 mV
- 751·8 × 103 V
- 75·18 mV
- 7·518 V
Correct Option: A
Given NA = 1: 106 atoms of silicon
| Therefore NA = | 5 × 1022 atoms/m3 | 106 |
So, NA = N0 = 5 × 1022 atoms/m3
ni = 1·45 × 1010 atoms/m3
= 1·45 × 1010 × 106 atoms/m3
= 1·45 × 1016/m3
| VT = | 25 mV at room temperature | 11,600 |
| Now, the contact potential V0 = VT In | ni2 |
| = 25 × 10–3 In | (1·45 × 1016)2 |
= 25 × 10–3 In 11·8906 × 1012
= 751·824 × 10–3 = 751·8 mV
Hence alternative (A) is the correct choice.
