Question

A Si and a Ge diode has identical physical dimensions . The band gap in Si is larger than that in Ge.On applying reverse bias,

• A. The reverse current in Ge is larger than that in Si.
• B. The reverse current in Ge is smaller than that in Si.
• C. The reverse current is identical in both cases.
• D. None of the above

Answer 1

The correct option is C The reverse current is identical in both cases.

In forward bias $pn$ junction the applied voltage required increases with increasing band gap.But,in reverse biased a small amount of current that flows through $pn$ junction, called the reverse saturation current is a constant and independent of applied voltage so,it is also independent of band gap and the band gap in $Si$ is larger than that in $Ge$, so on applying reverse bias, the reverse current is identical in both cases.