Environmental Engineering Reference
In-Depth Information
4.5.8
Further Experimental Evidence to Confirm the True
Structure of the Device
The observed results and interpretations presented in the above
sections provide strong supporting evidence for the proposed new
model based on Fermi-level pinning at metal/n-CdTe interface. The
following experiments have been carried out to further confirm the
new device structure [8].
Following the usual procedure to fabricate the device structure,
Au contacts and In/Ga contacts were made side by side on the same
sample, as shown in Fig. 4.11. The In/Ga contacts were made by
painting In/Ga eutectic at room temperature and then annealing
using a fine soldering iron tip to consume the top surface layer and,
hence, to form a good ohmic contact between In/Ga and the CdTe
layer. Various contact combinations, as labelled in Fig. 4.11, were
measured,andtheobservationsandconclusionsaresummarisedin
Table 4.2.
2
3
4
5
Au
In/Ga
1
CdTe
CdS
CG
Glass
Figure 4.11
The electrical contacts used to identify the location of
the rectifying interface. Au and In/Ga contacts are used side by side to
measure I-V curves. The measurement results and conclusions drawn are
summarised in Table 4.2. The CdS/CdTe device structures used to perform
this experiment produced conversion e
ciencies of approximately 10%.
The above measurements confirm the existence of a large
SchottkybarrierattheAu/CdTeinterfaceandthenon-existenceofa
considerablerectifyingcontactatthen-CdS/n-CdTehetero-junction.
