Editing Power semiconductor device (section)

==Research and development==

===Packaging===

The role of packaging is to:
* connect a die to the external circuit.
* provide a way to remove the heat generated by the device.
* protect the die from the external environment (moisture, dust, etc.).

Many of the reliability issues of a power device are either related to excessive temperature or fatigue due to thermal cycling. Research is currently carried out on the following topics:
* Cooling performance.
* Resistance to thermal cycling by closely matching the [[Coefficient of thermal expansion]] of the packaging to that of the silicon.
* The maximum [[operating temperature]] of the packaging material.

Research is also ongoing on electrical issues such as reducing the parasitic inductance of packaging; this inductance limits the operating frequency, because it generates losses during commutation.

A low-voltage MOSFET is also limited by the parasitic resistance of its package, as its intrinsic on-state resistance is as low as one or two milliohms.

Some of the most common type of power semiconductor packages include the TO-220, TO-247, TO-262, TO-3, D<sup>2</sup>Pak, etc.

===Improvement of structures===

The IGBT design is still under development and can be expected to provide increases in operating voltages. At the high-power end of the range, the MOS-controlled thyristor is a promising device. Achieving a major improvement over the conventional MOSFET structure by employing the super junction charge-balance principle: essentially, it allows the thick drift region of a power MOSFET to be heavily doped, thereby reducing the electrical resistance to electron flow without compromising the breakdown voltage. This is juxtaposed with a region that is similarly doped with the opposite carrier polarity (''holes''); these two similar, but oppositely doped regions effectively cancel out their mobile charge and develop a 'depleted region' that supports the high voltage during the off-state. On the other hand, during the on-state, the higher doping of the drift region allows for the easy flow of carriers, thereby reducing on-resistance. Commercial devices, based on this super junction principle, have been developed by companies like [[Infineon]] (CoolMOS products) and [[International Rectifier]] (IR).

===Wide band-gap semiconductors===

The major breakthrough in power semiconductor devices is expected from the replacement of silicon by a wide band-gap semiconductor. At the moment, [[silicon carbide]] (SiC) is considered to be the most promising. A SiC Schottky diode with a breakdown voltage of 1200&nbsp;V is commercially available, as is a 1200&nbsp;V [[JFET]]. As both are majority carrier devices, they can operate at high speed. A bipolar device is being developed for higher voltages (up to 20&nbsp;kV). Among its advantages, silicon carbide can operate at a higher temperature (up to 400&nbsp;°C) and has a lower [[thermal resistance]] than silicon, allowing for better cooling.