Molecular Beam Epitaxy 101a€¦ · Molecular Beam Epitaxy 101a Author: Faebian Created Date:...
Transcript of Molecular Beam Epitaxy 101a€¦ · Molecular Beam Epitaxy 101a Author: Faebian Created Date:...
Molecular Beam
Epitaxy 101a
CRYSTAL STRUCTURE Section 1.1
Planes and directions
Family Singular
{hkl} e.g. {100}
(hkl) e.g. (100), (010), (001), (10̅0), (010̅), (001)̅
<hkl> e.g. <100>
[hkl] e.g. [100], [010], [001], [10̅0], [010̅], [001]̅
Face centred cubic (FCC)
As-FCC Ga-FCC
http://www.dawgsdk.org/crystal/en/library/
Interleaved FCC
http://www.dawgsdk.org/crystal/en/library/
Zinc-blende
http://www.dawgsdk.org/crystal/en/library/zinc-blende#0000
Planes “top down”
The face of a fcc lattice is a {001} plane
[100]
[010]
Each face has 2 atoms per a2
Monolayer (ML) An atomic layer of a plane
• Atoms per cm2
– 2 atoms per a2 is a non-SI unit
– a for GaAs is 5.65338 Å
– a2 is therefore 31.961 Å2 or 0.31961 nm2
– 2 atoms per 0.31961nm2 is 6.258 atoms/nm2
– ...Or 6.258 x 1014 atoms/cm2
– One ML is 6.258 x 1014 Ga and As atoms/cm2
• Atoms per cm3 – 4 + (1/2 x 6) + (1/8 x 8) = 8 atoms per a3
– 4.428 x 1022 atoms/cm3
ML steps
Ga
Ga
As
As
As
a
a/2
[001]
[110]
Offcut and steps
• Ingot – Czochralski process
• Slice • Step density • 0.1°
– ~105 steps – ~150nm wide
Thin films on thick substrates Substrates and templates
GaAs/GaAs(100)
GaAs/Ge/Si