Gallium Nitride - Developments

Developments

High crystalline quality GaN can be obtained by low temperature deposited buffer layer technology. This high crystalline quality GaN led to the discovery of p-type GaN, p-n junction blue/UV-LEDs and room-temperature stimulated emission (indispensable for laser action). This has led to the commercialization of high-performance blue LEDs and long-lifetime violet-laser diodes, and to the development of nitride-based devices such as UV detectors and high-speed field-effect transistors.

High-brightness GaN light-emitting diodes (LEDs) completed the range of primary colors, and made applications such as daylight visible full-color LED displays, white LEDs and blue laser devices possible. The first GaN-based high-brightness LEDs were using a thin film of GaN deposited via MOCVD on sapphire. Other substrates used are zinc oxide, with lattice constant mismatch only 2%, and silicon carbide (SiC). Group III nitride semiconductors are in general recognized as one of the most promising semiconductor family for fabricating optical devices in the visible short-wavelength and UV region.

The very high breakdown voltages, high electron mobility and saturation velocity of GaN has also made it an ideal candidate for high-power and high-temperature microwave applications, as evidenced by its high Johnson's Figure of Merit. Potential markets for high-power/high-frequency devices based on GaN include microwave radio-frequency power amplifiers (such as used in high-speed wireless data transmission) and high-voltage switching devices for power grids. A potential mass-market application for GaN-based RF transistors is as the microwave source for microwave ovens, replacing the magnetrons currently used. The large band gap means that the performance of GaN transistors is maintained up to higher temperatures than silicon transistors. The first gallium nitride metal/oxide semiconductor field-effect transistors (GaN MOSFET) were experimentally demonstrated in 1993 and they are being actively developed.

In 2010 the first enhancement mode gallium nitride transistors became generally available. These devices were designed to replace power MOSFETs in applications where switching speed or power conversion efficiency is critical. These transistors, also called eGaN® FETs, are built by growing a thin layer of GaN on top of a standard silicon wafer. This allows the eGaN FETs to maintain costs similar to silicon power MOSFETs, but with the superior electrical performance GaN.