MBE

Here are two pictures that give an idea of what MBE means in reality.
First, just a schematic drawing showing the necessary parts.
Second, the real thing. The picture shows part of a MBE machine at the University of Delaware, used for making world-record multi-junction solar cells.
MBE system
Same thing from the University Tokyo:
mbe system
While it doesn't look particularly cheap, it is still possible to use MBE for low-cost mass production.
   

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go to 9.2.1 Light Emitting Diodes

© H. Föll (Semiconductor Technology - Script)