Molecular Beam

Epitaxy 101b

MBE SYSTEM COMPONENTS Section 1.2

MBE

• Substrate temperature • Effusion Cells

• Elemental sources fluxes • Flux control using shutters • Flux monitoring

• Very abrupt interfaces • RHEED in situ monitoring • Mass analyser • Cryogenic panels • Pumps • Vacuum gauges

Vacuum: Pumps

• Roughing

• Turbo

• Sorption

• Cryogenic

• LN2 cryogenic shroud

• Ion

• Diffusion

• Titanium Sublimation

4K

N

S

N

S

V+ V+

Epitaxy

• Ultrahigh vacuum conditions (base pressure ~10-10mbar) • Vaporised solid ultrapure elemental sources

• Group III: In, Ga, Al • Group V: (N), P, As, Sb, Bi •Dopants: Si and Be

• Condense onto a heated, rotated substrate

Knudsen Cells

• PBN crucible • Heater element • Thermocouple • Shutter

t/c

As cracker

• Ta crucible

• Heater elements

• Thermocouples

• Needle valve

Monitoring Ion gauge Beam flux monitor

• BEP

– Filament

– Grid

– Collector

+V

+V

-V

+V e

-V

THIN FILM GROWTH Section 1.3

• Frank-van der Merwe (2D) – Step flow – Islanding

• Stranski-Krastanov (S-K) • Volmer-Weber (3D)

Growth modes

Growth modes

• Frank-van der Merwe (2D) – Step flow – Islanding

• Stranski-Krastanov (S-K) • Volmer-Weber (3D)

• Frank-van der Merwe (2D) – Step flow – Islanding

• Stranski-Krastanov (S-K) • Volmer-Weber (3D)

Growth modes

• Frank-van der Merwe (2D) – Step flow – Islanding

• Stranski-Krastanov (S-K) • Volmer-Weber (3D)

Growth modes