Zhores l. Alferov

Layer by layer

A heterostructure consists of thin stacked layers of semiconductor materials (such as GaAs, AlGaAs, InP, InGaAsP, Si, SiGe) with different bandgaps. The layers can be as thin as a single atomic layer and as thick as several micrometres. The materials are generally selected so that their crystal structures fit one another.

High-speed electronics

Transistors for high-speed electronics require materials where the electrons can move very fast. The first detailed description of a heterostructure transistor was published by Kroemer in 1957. Nowadays, the different types of heterostructure transistor include the High Electron Mobility Transistor (HEMT) and the Heterojunction Bipolar Transistor (HBT) as the most common. They can be used at hundreds of GHz, which is at least ten times higher than possible with ordinary transistors. Heterostructure transistors may be integrated in small circuits known as Microwave Monolithic Integrated Circuits (MMICs) for more demanding applications.