Dear Somebodyfromanywhere,
I do not know precisely the answer to your first question regarding: Dr Taylor's initial motivation. His background suggests early contact with microprocessing and material science and certainly the thinking on the substrates used for chips early in their history though that the Gallium compounds were better semiconductors than Silicon by reason of their chemistry. Silicon, however, was cheap and easily available (Silicon is in essence sand and one of the most common elements on earth) earlier on and had a substantial potential for development. That potential is reaching its terminal limits now.
The reason that Gallium compound behave as better semiconductors is due to its chemistry, in particular, their molecular make-up. You will recall they are often referred to as 111 - V elements. This refers to their position in what is commonly known as the Periodic Table of Elements. This table indicates the atomic make-up of the elements. Gallium has 3 free electrons in the outer shell of its atoms and Arsenic and Nitrogen and Phosphorus are 3 short in their outer shells. When they are compounded (mixed together) these outer electrons are technically available to move around under the right circumstances and, therefore, when electrons move in this way a current flows. This can be controlled in such a way as to stop and start the flow using another external current. So you can create a transistor in Gallium Arsenide (as per POET) or Gallium Nitride or Phosphide because you can make them stop or start and you have the basis of a binary code.
All these substances have been used and my understanding is that Geoff Taylor's chips can use other substrates such as Gallium Nitride and well as Gallium Arsenide. One more thing, is that because of the electron availability and lack of obstruction in molecular terms within Gallium Arsenide then there is less resitance to electron flow and, as a result, less heat is produced because you can operate at lower voltages. Hence, the saving on batteries.
Sorry about the chemistry tutorial, I just hope it helps.
David
