Low Subthreshold Swing Double-Gate \beta -Ga2O3 Field-Effect Transistors With Polycrystalline Hafnium Oxide Dielectrics

• Published in: IEEE electron device letters 2019-08, Vol.40 (8), p.1317-1320
• Main Authors: Ma, Jiyeon, Yoo, Geonwook
• Format: Article
• Language: English
• Subjects: <italic xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">β -Ga₂O; Dielectrics; double-gate; Field effect transistors; Gallium; Hafnium oxide; Hysteresis; Logic gates; Temperature measurement
• ISSN: 0741-3106
• DOI: 10.1109/LED.2019.2924680

We demonstrate low subthreshold swing (SS) double-gate (DG) \beta -Ga 2 O 3 field-effect transistors (FETs) with polycrystalline hafnium oxide (HfO 2 ) gate dielectrics. The atomic layer deposited HfO 2 layer at an elevated temperature of 350 °C without post-deposition annealing has a polycrystalline structure. The threshold voltage is modulated from depletion- to enhancement-mode by independently controlled bottom-gate bias. The SS is reduced to as low as 64 mV/dec with mobility of 20 cm 2 / \text{V}\cdot \text{s} while maintaining a high ON/OFF ratio of 10^{{7}} and negligible hysteresis of 30 mV via double-gate operation. The device shows an ON/OFF ratio of 10^{{6}} and the SS of 320 mV/dec up to an operating temperature of 250 °C and the OFF-state breakdown voltage of 355 V. The demonstrated DG \beta -Ga 2 O 3 FETs with the polycrystalline HfO 2 layer is a promising structure for energy efficient high temperature device and circuit applications.