Band Gap Threshold Shift Scan - Semiconductor Physics: Bands, Doping, and Junctions Step by Step

Moving the band gap changes which photon rows are accepted. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Lower gap accepts and leaves excess

The photon stays at 6 joules. Moving the band gap to 4 joules gives accepted bit 1 and excess 2 joules.

\begin{array}{c}E=hf=2\cdot 3=6\ \mathrm{J}\\6\ \mathrm{J}\ >\ E_g=4\ \mathrm{J}\\\mathrm{accepted}=1\end{array}

Matching gap is the equality boundary

The photon stays at 6 joules. Moving the band gap to 6 joules gives accepted bit 1 and excess 0 joules.

\begin{array}{c}E=hf=2\cdot 3=6\ \mathrm{J}\\6\ \mathrm{J}\ =\ E_g=6\ \mathrm{J}\\\mathrm{accepted}=1\end{array}

Higher gap rejects the same photon

The photon stays at 6 joules. Moving the band gap to 8 joules gives accepted bit 0 and excess 0 joules.

\begin{array}{c}E=hf=2\cdot 3=6\ \mathrm{J}\\6\ \mathrm{J}\ <\ E_g=8\ \mathrm{J}\\\mathrm{accepted}=0\end{array}