GaN-Based Transistors for Power Electronic Applications
- Category: Electronic Devices
- Tags: daniel piedra, gallium nitride, tomas palacios
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Download as PDFWide band-gap III-nitride semiconductors have great potential for the next generation of power electronics. GaN high-electron-mobility transistors (HEMTs) in particular have attracted great interest due to their high breakdown electric field and high electron mobility. With lower conduction loss and higher switching frequency, GaN-based transistors can improve the efficiency and reduce the size of many power electronics systems.
The standard AlGaN/GaN HEMTs are depletion-mode transistors. However, normally-off transistors are preferred in power electronics. Recently, our group has developed a new normally-off tri-gate GaN metal-insulator-semiconductor-field-effect-transistor (MISFET) [1] . By using a three-dimensional tri-gate structure and a sub-micron gate recess, we achieve high performance normally-off GaN transistors with a breakdown voltage as high as 565 V at a drain leakage current of 0.6 μA/mm. The new tri-gate normally-off GaN MISFET has a maximum current density of 530 mA/mm and an on/off current ratio of more than 8 orders of magnitude with a sub-threshold slope of 86±9 mV/decade, as Figure 1 shows. We have also demonstrated a new multi-finger technology with higher yield and lower device resistance for InAlN/GaN HEMTs. A multi-finger device with gate width of 39.6 mm has an on-resistance (Ron) of 0.244 Ω and a maximum current of 18.5 A, as in Figure 2(a).
Finally, ion-implantation isolation technology has also been developed. A state-of-the-art 1800 V breakdown voltage with 2.2 mΩcm2 specific on-resistance has been achieved on AlGaN/GaN HEMTs on Si substrate (Figure 2(b)). Devices with ion-implantation isolation have higher breakdown voltage than devices using mesa-etching isolation, showing that ion-implantation isolation is a promising candidate for the next-generation high voltage GaN-based HEMT fabrication.
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- Figure 1: (a) Transfer characteristics of a tri-gate normally-off GaN MISFET and a standard planar-gate D-mode GaN MIS-HEMT. Both devices have Lgs = 1.5 μm, Lg = 2 μm, Lgd = 10 μm and W = 100 μm. (b) Three-terminal breakdown voltage (BV) measurement of the tri-gate normally-off GaN MISFET with Lgd = 10 μm at Vgs = 0 V.
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- Figure 2: (a) Id-Vd characteristic of a multifinger device with Wg = 39.6 mm and Ron = 0.244 Ω. (b) Three-terminal breakdown voltage as a function of Lgd for implantation and mesa devices. The inset shows the breakdown voltage at leakage current of 10 μA/mm
- B. Lu, E. Matioli and T. Palacios, “Tri-gate normally-off GaN power MISFET,” IEEE Electron Device Letters, vol. 33, no. 3, pp. 360-362, 2012. [↩]