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Gallium Nitride (GaN) High Power Electronics (FY11)
Director's Research Initiative
ARMY RESEARCH LAB ADELPHI MD SENSORS AND ELECTRON DEVICES DIRECTORATE
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This report covers work done for the Directors Research Initiative DSI on Gallium Nitride GaN High Power Electronics HPE in which GaN devices are assessed in comparison to those fabricated from silicon carbide SiC. We show that for low power applications less than 1500 V GaN diodes should have a lower on-resistance, and therefore less loss, than their SiC counterparts because the critical breakdown field and electron mobility are larger. We expect this will also be true for HPE GaN high electron mobility transistors HEMTs compared to SiC metal-oxide-semiconductor field effect transistors MOSFETs. Although a few GaN devices have been made that have properties that exceed those made from SiC, these devices cannot yet be manufactured. Our work suggests the dominant problem is contamination of the metal-organic chemical vapor deposition MOCVD films by the carbon in the trimethyl gallium TMGa. We suggest a better alternative is to grow the films by hydride vapor phase epitaxy HVPE, which requires that conducting GaN substrates be grown to reduce the on-resistance RON-SP for the back side diodes. We also show that dislocations appear to strongly affect diode properties such as the ideality factor, but their effect on the breakdown voltage appears to be a less significant problem than was previously thought.
APPROVED FOR PUBLIC RELEASE