Molecular Beam Epitaxy (MBE) is a controlled thermal evaporation process under ultrahigh vacuum. MBE allows extremely accurate layer thickness control - ultimately within one atomic layer. To grow the layer, elements like Ga, As, Si along with the dopant, are heated in separate cells. Collimated beams of these elements are directed onto the substrate surface. The temperature of the effusion cell controls the flux density. Abrupt changes in doping and composition can be obtained by controlling shutters in front of the individual cells. Using a very slow growth rate (<1µm/h), it is possible to make composition changes on the scale of one lattice constant. The two chamber system was designed for the deposition of compound semiconductors (V80H) and group IV elements (V80M). At present the V80H is used for the growth of diluted ferromagnetic semiconductor materials like GaMnAs and GaMnN. In V80M Si/SiO_x multilayer structures and epitaxial SnO₂ on sapphire heterostructures are processed.

Technical data

V-80H chamber

• type of molecular sources - 10, 30 and 200cc Knudsen cells
• maximum amount of cells - 8
• loaded elements - Ga, Mn, As, Si, Be
• Maximum substrate size 76 mm dia.
• Maximum substrate temperature - 800°C
• Base pressure 5x10^-11torr
• 15kV electron gun and screen for structural monitoring (RHEED)

V-80M chamber

• type of molecular sources - three 30 cc Knudsen cells, two 8kW E-beam evaporators, RF-plasma cell
• loaded materials - Ge, Sb, B₂O₃ in Knudsen cells, Si, Sn, SnO₂, SiO, Mo in E-beam evaporators
• available gases for RF plasma cell - O₂, H₂, N₂, Xe
• maximum substrate size 76 mm dia.
• maximum substrate temperature 900°C. Heater is resistant to oxygen ambient
• base pressure 1x10^-10torr
• 15kV electron gun and screen for structural monitoring (RHEED)

The loading chamber (between V80H and V80M chambers) is equipped with Auger electron spectrometer for surface chemical composition inspection.

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