\(\mathrm{C}\) and \(\mathrm{Si}\) both have the same lattice structure, having \(4\) bonding electrons in each. However, \(\mathrm{C}\) is an insulator whereas \(\mathrm{Si}\) is an intrinsic semiconductor. This is because:
1. in the case of \(\mathrm{C},\) the valence band is not completely filled at absolute zero temperature.
2. in the case of \(\mathrm{C},\) the conduction band is partly filled even at absolute zero temperature.
3. the four bonding electrons in the case of \(\mathrm{C}\) lie in the second orbit, whereas in the case of \(\mathrm{Si},\) they lie in the third.
4. the four bonding electrons in the case of \(\mathrm{C}\) lie in the third orbit, whereas for \(\mathrm{Si},\) they lie in the fourth orbit.
Subtopic:  Energy Band theory |
 72%
From NCERT
NEET - 2012
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\(\mathrm{p\text-n}\) photodiode is fabricated from a semiconductor with a band gap of \(2.5~\text{eV}.\) It can detect a signal of wavelength:
1. \(6000~\mathring{A}\)
2. \(4000~\text{nm}\)
3. \(6000~\text{nm}\)
4. \(4000~\mathring{A}\)  
Subtopic:  Energy Band theory |
 64%
From NCERT
AIPMT - 2009
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A p-n photodiode is made of a material with a bandgap of 2.0 eV. The minimum frequency of the radiation that can be absorbed by the material is nearly:

1. 10×1014 Hz

2. 5×1014 Hz

3. 1×1014 Hz

4. 20×1014 Hz

Subtopic:  Energy Band theory | Applications of PN junction |
 82%
From NCERT
AIPMT - 2008
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In the energy band diagram of a material shown below, the open circles and filled circles denote holes and electrons respectively. The material is a/an: 

1. p-type semiconductor

2. insulator

3. metal

4. n-type semiconductor

Subtopic:  Energy Band theory |
 73%
From NCERT
AIPMT - 2007
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