Combat Hybrid Power System Component Technologies Technical Challenges and Research Priorities (2002) / Chapter Skim
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4 High-temperature, Wideband Gap Materials for High-power Electric Power Conditioning
4 High-temperature, Wideband Gap Materials for High-power Electric Power Conditioning
Pages 31-40
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From page 31... ...
These inclucle higher temperature stability; higher chemical stability in extreme environments; higher thermal conductivity, resulting in reduced cooling requirements; and higher breakdown fielcI, which translates into more compact and higher frequency devices. These characteristics are especially desirable in high-power electronic cievices such as those used in the power conditioning systems of hybric!
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From page 32... ...
private investment, high-quaTity substrates are commercially available. The commercially available substrates, although not sufficiently defect-free for large area device fabrication, permit homoepitaxial layers to be (lepositecl in which high-power crevices, which require low-clefect materials, can be fabricated.
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From page 33... ...
are more practical, because defects at the gate insulator-conduction channel interface limit the switching performance of SiC MOSFETs produced for applications. At present, the world's first commercially available power device based on WBG materials is the SiC Schottky diode (600 V, 4-12 A)
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From page 34... ...
mentionecl previously, the c-plane wafers have micropipe defects that are generally perpenclicular to the c-plane wafer surface, ancl the clefect density is sufficiently large to prevent the fabrication of large-area crevices. Therefore, the use of low clefect density, epitaxial growths on the c-plane wafer surface have been pursuec3 for device fabrication.
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From page 35... ...
The (1 120) a-plane material is important in that the direction of micropipe defects are approximately parallel to the surface of the wafer and thus perpendicular to any applied electric field.
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From page 36... ...
Unipolar discrete devices are limited to a few square millimeters in area by the existing materials; current density ratings of 200 A/cm limit device current ratings to ~100 A To improve performance, micropipe and other material defect densities must decline while substrate diameter increases.
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From page 37... ...
that can be processed using existing etching techniques is available in large (limensions. The combination of high resistivit-Y and matched CTE in poly SiC makes it an ideal packaging material.
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From page 38... ...
The now-common LED traffic signal lights and rear auto tail lights are expanding markets for GaN LEDs, ant} interior lighting applications are also being pursued. The target for luminous efficiency in an LED is 120 lumens/watt, which can be compared to the luminous efficiency of a 38
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From page 39... ...
Current surface defect densities are greater than 108 cm-2; this is acceptable for LEDs, but not for laser diodes and other devices. The current goal is to reduce the defect density below ~ 05 cm-2.
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From page 40... ...
a-plane crystal orientation Improvement of science and technology of implantation, implantation activation, and metal-semiconductor metallurgy in wideband gap devices and materials For SiC devices, development of processes for high-resistivity poly SiC with a matched coefficient of thermal expansion Fundamental processing research to control defects in bulk GaN and A1N 40
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