Chemistry Reference
In-Depth Information
porosity is a parameter that reflects the combined effect of pore diameter and interpore
spacing, it may roughly be estimated from average pore size and interpore spacing.
Also, while pore diameter and interpore spacing are the properties of individual pores,
pore density and porosity are the properties of the PS layer. In essence, the physical
and chemical properties of PS are not determined by porosity, although some proper-
ties can be correlated with porosity under specific conditions.
The following are some general observations on the effect of various factors on
PS density.
1. PS density for both
p
and
n
types increases with increasing HF concentration
(Figs. 8.50 and 8.51)
35,41,48
2. The density of PS formed on
p
-Si decreases with increasing current density
as shown in Fig. 8.50.
32,36,50
On the other hand, the density of PS formed on
n
-Si first increases with increasing current density, reaches a maximum, and
then decreases as shown in Fig. 8.51.
32,35,36,41
The variation with current density
is larger at lower HF concentrations.
3. PS density of
p
-type silicon increases with increasing dopant as shown in Fig.
35,36,48
PS density of
n
-Si under front illumination increases with increas-
ing dopant concentration, reaches a maximum at about
8.52.
and then
