Green Power-Silicon-Carbide (SiC) Schottky Barrier Diodes

Silicon Carbide (SiC) Schottky Barrier Diodes

曾經的“中流砥柱”Si 功率元件已日趨面臨其發展的材料極限，難以滿足當今社會發展對於 高頻、 高溫、高功率、高能效、耐惡劣環境以及輕便小型化的新需求。 以 SiC 為代表的第三代半導體材料憑藉其優異屬性，將成為突破口，正在迅速崛起。

Nowadays, Silicon Carbide (SiC) and Gallium Nitride (GaN) are regular headline grabbers in the technical press. This is because devices constructed using these wide bandgap technologies are superior to their silicon counterparts across many critical metrics and open up new, previously unfeasible applications. This white paper describes the structure and applications of SiC diodes and explains their advantages over silicon devices. It then introduces a new range of SiC diodes developed by Futurewafer to have a thinner device structure and discusses the additional benefits these provide over standard Si diodes in power applications.

碳化矽相對於矽的優點

矽的特性差異 和 4H-SiC，這是主要用於商用電力電子設備如圖 1 所示。

Wide bandgap semiconductors materials have a larger energy  gap than conventional semiconductors like silicon. As a result,  SiC has -10x better dielectric breakdown field strength with a thinner drift layer for the same voltage rating. This leads to lower resistivity and better conduction performance with a smaller die size than other products with a similar voltage rating. In addition, the approximately 3.5x better thermal conductivity of SiC allows more power dissipation for a given chip area. The maximum operating temperature of SiC is also almost twice that of Si. While packaging is typically a limiting factor in continuous operation, the extra margin with SiC gives confidence during transient thermal events.

Additionally, because of the small die size, device self capacitance and the associated charge are lower for a given current and voltage rating. This, combined with the higher electron saturation velocity of SiC, enables faster switching speeds with lower losses.

與矽等傳統半導體相比，寬禁帶半導體材料具有較大的能量，差距更大。因此，對於相同的額定電壓，更薄的漂移層使SiC的介電擊穿場強提高了10倍。這導致降低電阻率和更好的導電性能，與具有相似電壓的其他產品相比晶片尺寸較小。此外，散熱性能提高約3.3倍。SiC的電導率在額定的晶片面積情況下允許更高的功耗。SiC的最高工作溫度也幾乎是Si的兩倍。雖然封裝通常是一個限制連續運轉的因素，但SiC的額外裕度在瞬態熱事件期間提供更佳的散熱條件。此外，由於晶片尺寸較小，對於額定的裝置自體電容和相關電荷較低。SiC擁有更高的電子飽和速度，可實現更快的開關速度，損耗更低。

SiC in Real World

The Advantages of Silicon Carbide

The highest performance silicon power diodes are Schottky barrier diodes. Not only do SBDs have the lowest reverse recovery time (t_rr) compared to the various types of fast recovery (fast recovery epitaxial), ultrafast recovery and super-fast recovery diodes, they also have the lowest forward voltage drop (V_F). Both of these parameters are essential to high efficiency. Table 1 shows a comparison of breakdown voltage, V_F, and trr for commonly available diodes. While Schottky barrier diodes have the advantage of low forward losses and negligible switching losses compared to other diode technologies, the narrow bandgap of silicon limits their use to a maximum voltage of around 200 V. Si diodes that operate above 200 V have higher V_F and t_rr.

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