Dissertation - FTP Directory Listing - University of Surrey

100Number of pixels1013000 3500 4000 4500 5000 5500Pixel values [DN]Figure 4.12 Histogram of dark pixel values for test structure C1The tests were repeated for C2 and the results are complied in the table belowPerformance parameterTest structureC1C2Conversion gain K (DN/e-) 1.19 ± 0.05 1.24 ± 0.05Quantum efficiency (%) 8.1 ± 0.5 7.9 ± 0.5Noise (e-) 14.4 ± 0.5 14.2 ± 0.5Linear full well (e-) 20700 ± 400 17900 ± 300Table 4.3 Summary of C test structure resultsAs can be seen the two structures show very similar performance in all areas, however C1 has a fillfactor of 35% whilst C2 only has FF = 8% so it was expected that C1 would have a higher quantumefficiency than C2 although the results show they are equal. C1 and C2 use the same type of diodesand capacitors as B2 and B4 respectively and the results from C1 and C2 are very similar to theresults of B2 and B4. Both C1 and B2 have fill factors of 35% but both show a lower than expectedquantum efficiency, C1 and B2 have diodes and the type of capacitor in common. But the type ofdiode is common to all four structures and B4 and C2 have QE reflective of their fill factors so it ismore likely that it is the type of capacitor used in C1 and B2, an accumulation capacitor, which issomehow causing the low QE measurement.51