Holey and Unholey Semiconductors

Abstract

Cooling electronic devices can often be necessary to optimize performance. Traditional approaches to cooling are typically based on thermodynamic cycles involving compression and expansion of refrigerant gases (such as Freon). The heat required for vaporization is drawn from the materials or the volume (for example, a refrigerator) that is to be cooled. Thermoelectric (TE) materials, in contrast, do not rely on chemicals or gases but rather on a special physical phenomena called the Peltier effect, which is explained in detail below (1). In TE materials, heat is not primarily transported by the lattice but by the electrical charge carriers—electrons or holes. Applying an electrical current through a TE material cools one end and transports the heat to the other end of the material or device. This has distinct advantages in that it is solid-state refrigeration, without moving parts and vibrations, and with quiet performance and the ability for localized “spot” cooling. This can be very important for many semiconducting and other electronic devices. But until recently, the efficiency of TE devices has been frustratingly low, and applications remain limited.