MSN 551 Notes

Epitaxial growth

Overview● Epitaxial and non-epitaxial growth● Cleanliness, UHV● MBE● MVPE● MOCVD● Atomic layer deposition● Application examples

http://www.eas.asu.edu/~vasilesk/

A typical MBE chamber● UHV● Loading● Cleaning● Heating● Analytical

tools● Film growth

monitoring

Basic MBE schematic

Knudsen effusion cell

Max operating temperature 1500 degs. C Heating method Tantalum foil Bakeout temperature to 250 degs. C Typical Power at 1500 degs.C 125 W Apertures 1 mm supplied optional 1.5, 2.0, 2.5, & 3.0 mm Crucibles ( Liners ) Graphite Crucible (liner) Pyrolytic Boron NitrideDensity 1.82 g/cc 2.15 g/ccOpen Porosity 8% 0%Capacity 0.5 cc 0.4 cc

Knudsen cell utilizes the principle of molecular effusion

The material to be deposited is heated to provide a suitable vapor pressure in an isothermal enclosure. Molecular effusion from an aperture in the end of the cell gives rise to a cosine intensity distribution. The deposition rate is extremely stable being determined by the temperature of the furnace which is accurately controlled with a PID controller.

Applications

Quantum dot laser material

Applications

Quantum cascade laser (far infrared laser)

Applications

Applications

Atomic Layer deposition● Monolayer by Monolayer growth● Self-limiting surface adsorption● Physically adsorbed monolayer formation● Surface reaction and monolayer deposition● Different than MBE● Perfect conformal coatings of many different

compounds

ALD example

Conformal