Schottky-Drain Technology for AlGaN/GaN High-Electron Mobility Transistors

Dept. of Electr. Eng. & Comput. Sci., Massachusetts Inst. of Technol., Cambridge, MA, USA
IEEE Electron Device Letters (Impact Factor: 2.75). 05/2010; 31(4):302 - 304. DOI: 10.1109/LED.2010.2040704
Source: IEEE Xplore


In this letter, we demonstrate 27% improvement in the buffer breakdown voltage of AlGaN/GaN high-electron mobility transistors (HEMTs) grown on Si substrate by using a new Schottky-drain contact technology. Schottky-drain AlGaN/GaN HEMTs with a total 2-??m-thick GaN buffer showed a three-terminal breakdown voltage of more than 700 V, while conventional AlGaN/GaN HEMTs of the same geometry showed a maximum breakdown voltage below 600 V. The improvement of the breakdown voltage has been associated with the planar contact morphology and lack of metal spikes in the Schottky-drain metallization.

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Available from: Edwin L. Piner, Feb 25, 2015
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    • "In spite of the outstanding electrical properties of GaN material, the main challenge is to improve reliability of GaN HEMTs [2]. Many researchers have put significant effort into improving the breakdown voltage (BV) of conventional lateral GaN HEMTs by employing field plates (FPs) [1], increasing the epitaxial-layer thickness [3] [4], doping the buffer with iron or carbon [5], inserting AlGaN buffer layer to the HEMT structure [6] [7], and use of Schottky contacts in drain [8]. Bin Lu et al [9] presented innovative technology to improve BV of GaN HEMTs to ∼1500 V by replacing silicon substrate with an insulating carrier wafer. "
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    ABSTRACT: A novel enhancement mode structure, a buried gate gallium nitride (GaN) high electron mobility transistor (HEMT) with a breakdown voltage (BV) of 1400 V–4000 V for a source-to-drain spacing (L SD) of 6 μm–32 μm, is investigated using simulations by Silvaco Atlas. The simulations are based on meticulous calibration of a conventional lateral 1 μm gate length GaN HEMT with a source-to-drain spacing of 6 μm against its experimental transfer characteristics and BV. The specific on-resistance R S for the new power transistor with the source-to-drain spacing of 6 μm showing BV = 1400 V and the source-to-drain spacing of 8 μm showing BV = 1800 V is found to be 2.3 mΩ · cm2 and 3.5 mΩ · cm2, respectively. Further improvement up to BV = 4000 V can be achieved by increasing the source-to-drain spacing to 32 μm with the specific on-resistance of R S = 35.5 mΩ · cm2. The leakage current in the proposed devices stays in the range of ∼5 × 10−9 mA mm−1.
    Full-text · Article · Oct 2014 · Semiconductor Science and Technology
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    • "The reason of V BK enhancement for Schottky and hybrid drain devices could be attributed to the smooth interface between the Schottky metal and the AlGaN barrier layer (or GaN cap layer) and lack of metal spiking [8]. In addition, the hybrid drain devices present even higher V BK than the pure Schottky drain structure. "
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    ABSTRACT: In this letter, a hybrid Schottky–ohmic drain structure is proposed for AlGaN/GaN high-electron-mobility transistors on a Si substrate. Without additional photomasks and extra process steps, the hybrid drain design forms a $\Gamma$-shaped electrode to smooth the electric field distribution at the drain side, which improves the breakdown voltage and lowers the leakage current. In addition, the hybrid drain provides an auxiliary current path and decreases the on -resistance, in contrast to the devices with a pure Schottky drain. Compared with the conventional ohmic drain devices, the breakdown voltage could be improved up to 64.9%, and the leakage current is suppressed by one order of magnitude without degradation of the specific on-resistance.
    Preview · Article · Jul 2012 · IEEE Electron Device Letters
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    • "For example, the breakdown voltages of AlGaN/GaN HEMTs with a total of 2-μm epitaxial layer on Si substrates are typically less than 800 V [4]–[6]. Several methods have been reported to improve the device breakdown voltage beyond 800 V, including increasing the epitaxial-layer thickness [5]– [7], doping the buffer with Fe or C [8], [9], using AlGaNbased buffer layers [3], and the use of Schottky-drain contacts [4]. Another alternative method is to use sapphire substrates. "
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    ABSTRACT: In this letter, we present a new technology to increase the breakdown voltage of AlGaN/GaN high-electron-mobility transistors (HEMTs) grown on Si substrates. This new technology is based on the removal of the original Si substrate and subsequent transfer of the AlGaN/GaN HEMT structure to an insulating carrier wafer (e.g., glass or polycrystalline AlN). By applying this new technology to standard AlGaN/GaN HEMTs grown on Si substrate, an AlGaN/GaN HEMT with breakdown voltage above 1500 V and specific on resistance of 5.3 mΩ·cm<sup>2</sup> has been achieved.
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