SCIENCE CHINA Information Sciences, Volume 62, Issue 6: 062403(2019) https://doi.org/10.1007/s11432-018-9503-9

Simulation of a high-performance enhancement-mode HFET with back-to-back graded AlGaN layers

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  • ReceivedFeb 9, 2018
  • AcceptedJun 21, 2018
  • PublishedJan 16, 2019


A novel three-dimensional hole gas (3DHG)enhancement-mode (E-mode) heterostructure field-effect transistor (HFET) isproposed and investigated. It features back-to-back graded AlGaN (BGA)barrier layers consisting of a positive-graded AlGaN layer and anegative-graded AlGaN layer, which form polarization gradient andsubsequently induce the three-dimensional electron gas (3DEG) and 3DHG inthe positive- and negative-graded AlGaN layers, respectively. The source anddrain are located at the same side of the metal-insulator-semiconductor(MIS) trench gate, and the source is in contact with the HfO$_{2}$ gateinsulator. First, the on-state current is significantly improved owing tothe high-density 3DEG in the positive-graded AlGaN. Next, the verticalconductive channel between the source and 3DEG is blocked by the 3DHG,thereby realizing the E-mode. The threshold voltage ($V_{\rm~th})$ can bemodulated by a partial doping conductive channel. Subsequently, a highbreakdown voltage (BV) is obtained, because the polarization junction formedby the polarization charges assists in depleting the drift region in theoff-state. Next, the BGA-HFET is smaller than the conventional HFET(Con-HFET) owing to the special location of the source. The BV of theproposed HFET sharply increases to 919 V from 39 V of the Con-HFET with thesame gate-drain spacing, and the saturation drain current is increased by103.5%


This work was supported in part by National Natural Science Foundation of China (Grant Nos. 51677021, 61234006), National Defense Science and Technology Project Foundation of China (Grant No. 1100395), and Fundamental Research Funds for the Central Universities (Grant No. ZYGX2014Z006).


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