Silicon Carbide and Gallium Nitride Set to Oust Silicon Circuits

If the history of technology has taught us anything in the field of microelectronics, it's that silicon is a winner. It has displaced most other materials, and only been kept out of applications such as photonics by physical properties that make it innately unsuitable. Where silicon can compete directly with materials that offer better nominal properties, it almost always wins. However, when it comes to power electronics, silicon may well have met its match.

As a material for power electronics, silicon has done quite well, but it has a weakness: when hit with a high voltage, it breaks down and starts to conduct uncontrollably. If power is not removed from the device it will simply burn itself to death, with a strong likelihood of roasting the other electronics that it was meant to protect. It is possible to boost the breakdown voltage – the point at which the transistor stops being able to control power – but this leads to higher resistance when switched on, which means more heat and power wasted.

To deal with the breakdown issue, while working at General Electric in the early 1980s Indian electrical engineer Dr B Jayant Baliga invented the insulated-gate bipolar transistor (IGBT) – a hybrid of the two most commonly-encountered types of transistor used now. For the most part, it behaves like the bipolar transistor that was first invented by William Shockley in the 1950s; but it has a gate, sitting behind a fairly thick layer of insulation, much like the metal-oxide semiconductor field-effect transistor (MOSFET) used in every computer.

This blended design has made it the power device of choice where breakdown is a problem. A hybrid electric car may have tens of IGBTs that are used to convert battery power into drive power – and back again. iAbrasive report.

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