TABLE OF CONTENTS 
This figure shows the evolution of modern power semiconductor devices with the year of commercial introduction and symbol on the right of each. These power devices constitute the heart of modern power electronics apparatuses and they are almost exclusively based on silicon material. It is no exaggeration to say that today's power electronics evolution has been possible primarily due to device evolution. Again, power semiconductor evolution has closely followed the evolution of microelectronics. Researchers in microelectronics have worked relentlessly to improve semiconductor processing, device fabrication, and packaging, and these efforts have contributed to the successful evolution of so many exotic power devices. Although basically they are on and off switches, practical devices are far more complex, delicate, and "fragile." Thyristors (or silicon-controlled rectifiers) and triacs are essentially the forerunners of modern power semiconductor devices, which operate mainly on a utility system and contribute to power quality and lagging power factor problems. GTOs and IGCTs (or GCTs) are high-power gate-controlled devices that are used in multi-megawatt applications. The BJT, once a very important device, has become obsolete. Power MOSFETs and IGBTs are self-controlled insulated-gate devices that are extremely important today. In particular, the invention of the IGBT in 1983 and its commercial introduction in 1985 have been important milestones in the history of power devices. An SIT is the solid-state equivalent of the vacuum triode; it has a high conduction drop and will not be discussed further. SiC devices with large band-gap semiconducting...
