Question

The band gap for a pure semiconductor is $2.1eV$. The maximum wavelength of a photon which is able to create a hole-electron pair is nearly :

• A. $600nm$
• B. $590nm$
• C. $400nm$
• D. $200nm$

Answer 1

The correct option is B $590nm$

Band gap $=2.1$ $eV$
$\Rightarrow \frac{hc}{\lambda }>2.1eV$

where, $h-$ Planck's constant
$c-$ speed of light

$\Rightarrow \lambda >\frac{1240}{2.1}$

$\Rightarrow \lambda >590nm$