Biomedical Engineering Reference
In-Depth Information
Step C—Finally, the binding energy
E
B
is determined. For each value of
electric field
F
⊥
:
C1: Determine β
e
and β
h
for Equation 3.30. This is done by minimizing
Equation 3.31 with respect to β.
C2: Using a value of λ and the above values of
N
2
(β) calculate the value of
E
PE
r
by performing the double integration over
z
e
and
z
h
in Equation 3.32.
C3: Calculate
E
EE
r
using Equation 3.29.
C4: Repeat steps C2 and C3, adjusting λ to minimize
E
B
.
C5: Start at step C1 for the next field value.
Again, it is useful to use look-up tables for parts of Step C—in particular for
the values of Equation 3.33.
3.11.7 Example: Fabrication of MQW Oscillator
An MQW could be fabricated from GaAs/AlGaAs heterostructure such as
that shown in Figure 3.25. This structure would require about five mask and
fabrication steps. The thin optical window, with no field applied perpendicu-
lar to the QW junction layers, will be transparent to a wavelength—denoted
λ
low
—of slightly lower energy than the absorption peak. Application of a filed
will shift the absorption peak to lower energies and the window will become
opaque to the incident wavelength λ
low
. This operation, depicted in Figure
3.26 [41] shows the transmission of the device as a function of the applied bias.
The proposed vertical material structure is shown in Figure 3.27 [46].
Figure 3.28 shows a photoluminescence scan of the material taken at room
temperature (~300 K). Various important features and their wavelengths and
95 µ
Light in
Si
3
N
4
Au contact
p
+
Semiconductor
contact
Si
3
N
4
i MQW active
0.965 µ
n
+
Semiconductor contact
n
+
GaAs substrate
Light out
Au/Sn contact
FIGURE 3.25
Optical QW oscillator modulator.
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