ABSTRACT

Once an ingot of semiconducting material has been produced, it must pass through several processing steps before it can be fabricated into a detector. These are, in order:

1. Thermal annealing 2. Cutting 3. Lapping and polishing 4. Etching 5. Cleaning

Following these preparatory steps, the crystal is contacted and characterized. Figure 3.1 shows the entire sequence of producing a detector, from the initial material synthesis to detector

characterization. The type and degree of processing depend on the mechanical properties of the material being processed. For example, group III-V materials are generally mechanically robust with hardness values of more than 500* kgf mm-2 on the Knoop microhardness scale (see Appendix E). These materials can therefore withstand a lot of fairly robust mechanical treatment without introducing a disproportionately large number of defects into the crystal, whereas groups II-VI and I-VII materials tend to be mechanically soft (Knoop hardness values of <~100† kgf mm-2). For these latter materials, chemical treatments are preferred because mechanical processing, such as lapping and polishing, can introduce more damage than is removed.