Can somebody please explain the purpose of this SiO2-layer?

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Thank you!

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    $\begingroup$ An inert layer protection from the atmosphere/dust/cleaning agents (or whatever medium the diode comes into contact with) that transmits light. Doped silicon can easily change its properties when it comes into contact with the wrong kind of material. $\endgroup$ – Sebastian Riese Jun 13 '18 at 11:03
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    $\begingroup$ @sebastianriese is right, such a layer is called "passivation" because it keeps the layer underneath from being chemically "active". $\endgroup$ – niels nielsen Jun 13 '18 at 21:26
  • $\begingroup$ Ok, thank you! So why is it then not totally wrapped with SiO2? $\endgroup$ – Ben Jun 14 '18 at 10:13

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