I thought you might like to know:

Gallium is an element obtained as a by product of the production of metals such as Alumuninium and Zinc. Although an element it does not occur naturally. There is more gold in the world than Gallium and its availalbility is a little more than 1M tonnes, it can and is frequently recycled. One characateristic it has a low melting point and will melt to a liquid (like Mercury) in your hand.

When it is mixed with Arsenic (which is much more abundant) it hardens and produces Gallium Arsenide; it can be made into wafers. These wafers are brittle compared to a Silicon wafer and have to be handled with care but their thickness is altered to make this less of a problem. Gallium Arsenide can be sprayed when heated onto a substrate (a flat surface of material that is less brittle) in a process called Molecular Beam Epitaxy to produce wafers (MBE - its the machine that was shut down for maintenance recently at the University of Conneticut).

The 8 inch wafer is a very common standard for mass production in fabs (factories that make microprocessors). It is more efficient to increase the size of the wafer but, as you do so, you increase failure because of gravitational effects and other factors. This introduces more production costs and there is a cost and benefit equation to increasing the diameter. You will be absolutely delighted to read that 8 inches (200 mms) is the best compromise between size and production cost.

So there, at last, I have got it off my chest. Brittleness is an issue but highly likely to be surmountable in mass production.

In 1 week I will write again on chip production. For homework please ask your parents to arrange a fat fryer and some Sunflower oil.

David