fix the link

src/14_doping_and_devices.md

@@ -251,7 +251,11 @@ For that we consider a doped semiconductor in the extrinsic regime.
 ### Exercise 4: Quantum well heterojunction in detail
 A quantum well is formed from a layer of $GaAs$ of thickness $L$, surrounded by layers of $Al_{x}Ga_{1−x}As$.
 
-![Quantum Well](https://commons.wikimedia.org/wiki/File:Quantum_well.svg#/media/File:Quantum_well.svg)
+![Quantum Well](https://upload.wikimedia.org/wikipedia/commons/4/45/Quantum_well.svg)
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+??? info "source"
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+    Vectorised by User:Sushant savla from the work by Gianderiu - [Quantum well.svg](https://commons.wikimedia.org/w/index.php?curid=73413676), [CC-BY-SA 3.0](https://creativecommons.org/licenses/by-sa/3.0 "Creative Commons Attribution-Share Alike 3.0").
 
 You may assume that the band gap of the $Al_{x}Ga_{1−x}As$ is substantially larger than that of $GaAs$.The electron effective mass in GaAs is 0.068 $m_{e}$ whereas the hole effective mass is 0.45 $m_{e}$ with $m_{e}$ the mass of the electron.