Substrate (also called a
wafer) is a solid (usually
planar) substance onto which a layer of another substance is applied, and to which that second substance adheres. In
solid-state electronics, this term refers to a thin slice of material such as
silicon,
silicon dioxide,
aluminum oxide,
sapphire,
germanium,
gallium arsenide (GaAs), an
alloy of silicon and germanium, or
indium phosphide (InP). These serve as the foundation upon which electronic devices such as
transistors,
diodes, and especially
integrated circuits (ICs) are deposited.