Question

a) What are the two major reasons why III-V materials are more difficult to process than silicon?

b) What is the liquid that is used as the solvent in liquid phase epitaxy of III-V materials?

Answer 1

One reason why I think III-V is more difficult to handle is because of their brittle nature which makes them hard to work on. Other reasons include abundance and cost. No natural oxide as in silicon i.e. it does not grow native oxide which is equivalent to SiO2.The single crystal GaAs substrate has higher production cost. GaAs wafers are more brittle compare to Silicon wafers.
Small size (about 4") ingots.GaAs is made of mixture of two metals Ga (Gallium) and As (Arsenic). Gallium is rarer than gold and it is byproduct of other metals such as aluminium and zinc. Arsenic (As) is not rare but it is poisonous.

As a solvent quite often Gallium is used in this case. Another frequently used substrate is Indiumphosphide InP. However also other substrates like glass or ceramic can be applied for special applications. To facilitate nucleation, and to avoid tension in the grown layer the thermal expansion coefficient of substrate and grown layer should be similar.