Physics of semiconductor power devices

Semiconductor power devices are designed to rapidly switch or amplify high currents, to support high voltages, and to control electric power. Because of these requirements, their topographies and structures are different from those of small-signal devices. Specific designs are the result of the understanding of the physics of p-n junction HV breakdown, gain variation at high currents, current instabilities, etc. After introducing elementary semiconductor structures, the author reviews the basic principles of the operation of bipolar and field-effect power transistors and thyristors. This is followed by a discussion of phenomena of special interest for power devices; junction avalanche breakdown, the effect of the current level on the current gain, dynamic and static behaviour at high currents and thermal properties and instabilities. The review includes recent advances in device physics and introduces the reader to new methods of improving device performance. Power is a relative concept-at microwave frequencies at few watts is a very large quantity; this review therefore includes a section on microwave power devices.