= Solution
With conventional <electric current> defined into the positive terminal, an ideal junction has
$$
I=I_0\left[\exp\!\left(\frac{qV}{n k_BT}\right)-1\right].
$$
The reverse-bias branch tends to \b[$-I_0$] before breakdown. In <forward bias> the <electric current> rises exponentially; a visibly sharp “turn-on” is a convenient operating description rather than a discontinuity in the equation. A powered <LED> emits in \b[quadrant I], where $V>0$, $I>0$ and the device absorbs electrical <power> $VI$. Strong reverse breakdown lies outside the ideal curve below.
\Image[/past-exam-of-the-mphil-in-micro-and-nanotechnology-enterprise-course-of-the-university-of-cambridge/2021/paper-1-diode-iv.png]
{title=Ideal diode characteristic with reverse saturation and forward LED operation}
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