relatively low breakdown strength in conventional SiN passivation is the bottleneck in this case. Buffer leakage is We report ultra high voltage AlGaN/GaN another limiting factor that has hindered the projected heterojunction transistors (UFETs) on sapphire with thick increase of the breakdown voltage. Thus, reported off-state poly-AlN passivation. Extremely high blocking voltage of breakdown voltage of AlGaN/GaN UFETs maintaining low 8300V is achieved while maintaining relative low specific on-state resistance has been below 1900V [1-6] at highest to on-state resistance (Ron-A) of 186mQ*cm2. Via-holes the best of our knowledge. through sapphire at the drain electrodes enable very efficientIn this paper, we demonstrate ultra high breakdown layout of the lateral HFET array as well as better heat voltages of AlGaN/GaN HFETs using thick poly-crystalline dissipation.AlN (poly-AlN) passivation combined with field plates. The poly-AlN gives high breakdown strength underneath the Introduction field plates together with better heat dissipation suppressing the effect of the surface traps that would cause so-called AlGa/GaNUFEs ar widly nvesigatd fr fuure
In this paper, recent advances of GaN transistors on Si for switching and high-frequency applications are reviewed. Novel epitaxial structures including superlattice interlayers grown by metal organic chemical vapor deposition (MOCVD) relieve the strain and eliminate the cracks in the GaN over large-diameter Si substrates up to 8 in. As a new device structure for high-power switching application, Gate Injection Transistors (GITs) with a p-AlGaN gate over an AlGaN/GaN heterostructure successfully achieve normally-off operations maintaining high drain currents and low onstate resistances. Note that the GITs on Si are free from current collapse up to 600 V, by which the drain current would be markedly reduced after the application of high drain voltages. Highly efficient operations of an inverter and DC-DC converters are presented as promising applications of GITs for power switching. The high efficiencies in an inverter, a resonant LLC converter, and a point-of-load (POL) converter demonstrate the superior potential of the GaN transistors on Si. As for high-frequency transistors, AlGaN/GaN heterojuction field-effect transistors (HFETs) on Si designed specifically for microwave and millimeter-wave frequencies demonstrate a sufficiently high output power at these frequencies. Output powers of 203 W at 2.5 GHz and 10.7 W at 26.5 GHz are achieved by the fabricated GaN transistors. These devices for switching and highfrequency applications are very promising as future energy-efficient electronics because of their inherent low fabrication cost and superior device performance.
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