In modern computers, bipolar semiconductor chips are often used in the arithmetic-logic unit. Which material is used for the slower and less expensive primary storage section?

Bipolar semiconductor chips (using ECL or TTL logic) are fast but expensive and power-hungry, making them suitable for ALU operations where speed is critical. MOS (Metal-Oxide Semiconductor) technology is slower but much cheaper, allows high-density integration, and is ideal for large primary memory (RAM) storage. Silicon and Germanium are raw materials, not specific technologies.