Biomedical Engineering Reference
In-Depth Information
Fig. 11.13
Generation rate of
F
o
along with the rising edge of the modulated laser pulse
field as opposed to the falling edge as shown in Fig.
11.11
a. With our data analysis
we observed that the rise time of the optically generated electric field followed
the positive edge of the laser pulse which has a rise time of 7-8
sasshown
in Fig.
11.13
. Therefore, unfortunately, with our current experimental setup we
were unable to determine the rise time of the optically generated electric filed, but
we can put an upper bound of 7-8
s. This can be interpreted as the generation of
the optically generated electric field having a frequency approaching MHz, whereas
the decay frequency falls within the KHz range.
We also measured the decay time of the optically generated electric field for
above the WL laser excitation powers of 0.3 and 0.6 mW (Fig.
11.14
). As we
increase the laser excitation power more e-h pairs contribute to the creation of
F
o
,
which can be seen as a larger variation of the peak energy values for the first two
data points, corresponding to a delay time of 0
s. But, as the charge carriers tunnel
out of the device the separation of the data points becomes smaller and subsequently
ends up at the same end point. However, the decay rate was found to remain in the
range of 125-137
s. This indicates that for the powers measured, the number of
electrons and holes created does not effect the response time of
F
o
.
