Molecular Beam Epitaxy (MBE). By Mohammad Junaebur Rashid, PhD. Post Doctoral Researcher. Solar Energy Research Institute ( SERI ) , University of Kebangsaan Malaysia ( UKM ) . Outline. Introduction. What is epitaxy?. Different epitaxy techniques. Molecular Beam Epitaxy (MBE).
Mohammad Junaebur Rashid, PhD
Post Doctoral Researcher
Solar Energy Research Institute (SERI),
University of Kebangsaan Malaysia (UKM).
Overlayeris called an epitaxial film or epitaxial layer.
Leads to unmatched lattice parameters.
Causes strained or relaxed growth lead to interfacial defects.
Effect on the film
Altered the electronic, optic, thermal and mechanical properties of the films.
Allows for optoelectronic structures and band gap engineered devices.
In-plane lattice mismatch:
where, afilm is the lattice parameter of the film and
asubis the lattice parameter of the substrate
The semiconductor is dissolved in the melt of another material (example: InP)
Schematics of MBE
In-situ Measurement System
(Beam flux monitor)
Sample Load Lock
(In-situ Measurement System)
RIBER 21 MBE systems: 8 sources (Al, Ga, C, NH3, Si, SiH4)
High resolution TEM of the lattice image shows the sharp interface between AlN and Si(111)
Nearly atomically abrupt transition from one material to another.
Mean free path for N2molecules at 300 K
(chevron like shape)
Temperature range 450°C ... 1400°C
[Substrate temperature is one of the key parameters during epitaxial growth.
→ Influences the growth rate, the composition of ternary and quaternary compounds and the doping level.
→ Impact on the quality of the grown layer and its roughness, thereby influencing the performance of devices based on such epitaxial layers.]
LAYTEC curvature measurement system based on two parallel laser beams (635 nm)
Light beams send nearly perpendicular to the surface in the center region of the wafer while rotating the wafer (8 – 10 rpm).
Curvature range: from -7000 km-1 (convex) to +800 km-1 (concave)
D = displacements of two laser beam, R = radius of curvature,
L = distance between the layer and detectors,
S = displacements of detected signals, W = wafer diameter
M = biaxial modulus and h = thickness.
Subscripts f and s referring to the film and substrate.
(Deduced from Stoney’s equation)
[Valid for hf/ hs << 1 and for small value of stress (linear approximation). For large bending non-linear theory will be applicable.]
Growth rate, layer thickness and roughness
This interaction depends on the type of adatoms, the substrate, and the temperature of the substrate.
Behavior of adatoms in the surface diffusion process
(Layer & island growth mode)