Chemistry Reference
In-Depth Information
and
where
r = x
+ is the ionized donor density,
q
is the electronic charge, is the
radius of curvature of the interface, and is the space charge layer width. According
to Eq. (8.10) the field strength of a curved surface increases considerably when the
radius of curvature is close to or smaller than the width of the space charge layer of a
flat surface. Figure 8.64 shows the effect of radius of curvature on the energy band
diagram with a potential drop of 5V across the space charge layer of an
n
-Si under an
anodic bias. Clearly the potential drops more sharply for a smaller radius of curvature
and the width of the space charge layer is considerably reduced. As a result, the field
in the space charge layer is greatly increased, for example, the field is about 4 times
higher for a curved surface with a radius of curvature of 1/5
than that for the
