Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA

Heteroepitaxial Growth of III-V Semiconductor on Silicon Substrates
a lower additional energy barrier (E s ) to come down the edge to a lower terrace.
From the mentioned kinetic parameters the diusion coecient is probably the
most important parameters. It determines the average distance an atom can
travel on at surface before being trapped. This distance is the surface diusion
length (l D ) and can be dened by Eq. 3.6 [35].
l D = √ D s τ (3.6)
Where τ is the residence time before re-evaporation. The surface diusion coef-
cient is generally expressed as:
D s = νa 2 exp ( −E A
K B T ) (3.7)
Where E A is the activation energy for diusion, ν is the attempt frequency
and a is the characteristic jump distance. From Eq. 3.7 it is clear that deposition
temperature is important because it controls the diusivity of the adaoms
[35]. Therefore, the growth modes in real systems far from equilibrium will be
controlled mostly by these kinetic factors and partially by the thermodynamics
factors.
Experimentally, the distinction between three classical growth modes is well
known and classied to three growth regimes: Frank-van der Merwe (FM) (layers
growth mode), Volmer-Weber (VW) (islands growth mode) and Stranski-
Krastonov (SK) (mixed growth mode layers and islands) as illustrated in Fig. 3.2.
In addition to the three well-known epitaxial growth modes mentioned above
there is a fourth one, which is the step-ow growth mode as already mentioned
in section (Sec. 3.2.1). The study of lm growth typically involves the deposition
of a controlled amount of atoms onto a well characterized crystalline substrate at
a prescribed set of growth conditions.
In the case of Frank-van der Merwe (FM) (layer by layer growth mode): Layer
growth is observed when the binding energy between the lm and substrate is
stronger than the binding force between the lm particles. However, in this case
a uniform monolayer of material is deposited in 2D forming a planar sheets as
long as the the binding energy is decreased toward the bulk crystal value, the
layer growth is sustained [36]. However, during FM growth mode a new layer is
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