3D Time-of-flight distance measurement with custom - Universität ...
3D Time-of-flight distance measurement with custom - Universität ...
3D Time-of-flight distance measurement with custom - Universität ...
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62 CHAPTER 3<br />
Very special processes avoid the reduced blue response by thinning the substrate<br />
to only several tens <strong>of</strong> microns, which is a quite complicated and expensive<br />
process. Such CCDs are illuminated from the back side and usually have a very<br />
good quantum efficiency.<br />
Quantum efficiency in %<br />
100<br />
90<br />
80<br />
70<br />
60<br />
50<br />
40<br />
30<br />
20<br />
10<br />
0<br />
Poly 2 Poly1<br />
400 600 800<br />
Wavelength in nm<br />
1000<br />
Figure 3.10 Measurement <strong>of</strong> quantum efficiency for poly1 and poly2 photogates<br />
realized in Orbit 2.0µm CMOS/CCD process. [HEK].<br />
3.1.3 Transport mechanisms for charge carriers<br />
Basically there are three independent transport mechanisms for free charge<br />
carriers in the semiconductor (Figure 3.11):<br />
Self-induced drift<br />
1. Self-induced drift<br />
2. Thermal diffusion<br />
3. Drift due to an electric field.<br />
Self-induced drift is based on the coulomb forces between free charge carriers <strong>of</strong><br />
the same polarity. It makes the charge carriers tend to move away from each other.<br />
In practice self-induced drift only contributes significantly to the overall charge
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