Why were germanium and silicon important materials for early transistors?
Negative-channel metal-oxide semiconductors (NMOS) employ a positive secondary voltage to switch a shallow layer of p-type semiconductor material below the gate into n-type. For positive-channel metal-oxide semiconductors (PMOS), all these polarities are reversed. NMOS transistors are more expensive, but faster, than PMOS transistors.
Germanium and silicon were essential to the development of early transistors because they are semiconductors, materials whose electrical properties can be precisely controlled by adding minute amounts of other elements, a process known as doping.12
Germanium
Early transistors utilized germanium primarily because purification methods required to achieve the necessary material quality were established during and shortly after World War II. Its semiconducting properties made it highly valuable for early electronic devices.13
Silicon
By the late 1950s, silicon became the preferred material for several reasons:
* Abundance and Cost: Silicon is much more abundant than germanium, making it less expensive.1
* Thermal Stability: Silicon retains its semiconducting properties at significantly higher temperatures than germanium, allowing devices to operate up to 200 °C (400 °F).1
* Manufacturing Advantage: Crucially, silicon forms a stable, insulating oxide film when heated. This film acts as a mask during photolithographic manufacturing, enabling the creation of tiny, low-cost transistors and integrated circuits.1