Biomedical Engineering Reference
In-Depth Information
HF
0 nm GaAs
7 nm GaAs
a
b
c
200 nm
d
5
0
-5
(a)
(b)
(c)
(a)
(b)
(c)
-10
[1-10]
[110]
200
400
600
800
200
400
600
800
Distance (nm)
Distance (nm)
Fig. 1.14
AFM topography images of a nanohole after (
a
) HF treatment, (
b
)HF
+
(H
+
As
4
)
treatment, and (
c
)HF
As
4
) treatment followed by the growth of a 7-nm-think GaAs buffer
layer. The nanoholes profiles along [1
+
(H
+
1 0] and [1 1 0] crystallographic directions are shown in
(
d
). Adapted from [
22
]. Copyright 2009 Institute of Physics
−
Tabl e 1. 2
Average values of the relative differences in depth and widths along
[110] and [1
1 0] directions of the initial nanoholes (after HF treatment) and
the nanoholes obtained with and without a 7-nm-thick buffer layer growth
GaAs buffer layer
thickness (nm)
−
Width [1 1 0] (%)
Width [1
−
1 0] (%)
Depth (%)
0
+
1
−
18
+
20
7
+
32
−
13
−
11
facets inside the nanoholes that, under certain growth conditions, incorporate Ga
atoms preferentially with respect to (0 0 1) surfaces. Nevertheless, for both surface
preparation processes (with or without GaAs buffer layer growth) the patterned
nanoholes are preserved before the InAs deposition is performed. Similar qualitative
results are obtained for nanoholes corresponding to initial oxides with a “double
structure.”
The dependence of InAs nucleation process on the crystallographic orientation
of the nanoholes can be studied fabricating oxide lines (120 nm width, 500 nm
length, and 8 nm height) with orientations along the [1
−
1 0], [0 1 0] and [1 1 0]
