Molecular Beam Epitaxy (MBE) is an advanced ultra-high-vacuum facility (basic pressure 10-13 bar) to make compound semiconductor materials with great precision (< 0.01 nanometer) and purity (>99.99999%).

These materials are layered one on top of the other to form semiconductor devices such as transistors and lasers.

In this process beams of atoms or molecules in an ultra-high vacuum environment are incident upon a heated crystal that has previously been processed to produce a nearly atomically clean surface.

One or more evaporated beams of atoms react with the substrate to yield a film.

Semiconductor and dopant sources are arrayed around the substrate.

Source beams are obtained by thermal evaporation from high purity elements which are placed in crucibles known as effusion cells.

Growth rate in MBE is proportional to arrival rate of flux at substrate.

Shutters control exposure to each species which are situated at the mouth of cells. This shutter is operated pneumatically.

The sources can be solid source (for arsenide compounds) or gas source (for phosphorus compounds).