8. Integral Diode

The power MOSFET device is often used in circuits which produce current flow through the structure in the third quadrant of its i − v characteristics. Two prominent examples of such circuits are the voltage regulator module (VRM) used to deliver power to microprocessors in computers and the H-bridge motor control circuits used to achieve adjustable speed drives. One of the advantages of the power MOSFET structure is an inherent reverse conducting diode within the structure which allows carrying current in the third quadrant of operation. Unfortunately, the switching speed of this diode is very slow in as-fabricated devices producing excessive power losses that limit the circuit operating frequency. This problem was first overcome by the use of electron irradiation to control the minority carrier lifetime to achieve improved reverse recovery characteristics for the body diode in the power D-MOSFET structure [1].