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High-Performance GaN HEMTs with I <inf>ON</inf>/I <inf>OFF</inf> ≈10<sup>10</sup> and Gate Leakage Current <10<sup>−11</sup> A mm<sup>−1</sup> Using Ta<inf>2</inf>O<inf>5</inf> Dielectric
Journal
Physica Status Solidi (A) Applications and Materials Science
ISSN
18626300
Date Issued
2022-06-01
Author(s)
Upadhyay, Bhanu B.
Surapaneni, Sreenadh
Yadav, Yogendra K.
Bhardwaj, Navneet
Suvachintak, Netaji
Ganguly, Swaroop
Saha, Dipankar
Abstract
Herein, Ta2O5 high-k gate dielectric-based GaN high electron-mobility transistors (HEMTs) with a high I ON/I OFF ratio and low gate leakage current are demonstrated without any significant deterioration of the other performance parameters. Ta2O5 with an average surface roughness of 1.8 nm and a dielectric constant of ≈26 are grown by sputtering and annealing in O2. The bandgap, valence, and conduction band offsets with Al0.3Ga0.7 N are 4.85, 0.24, and 0.61 eV, respectively. The reverse gate leakage current at −7 V is observed to be 1.2 ×10−10 A mm−1 for 5 nm and <1.0×10−11 A mm−1 for 20 and 30 nm oxide thickness compared to 5.0 × 10−6 A mm−1 for the control sample. This current is among the lowest ever reported for GaN-based oxide-HEMTs without significantly sacrificing other performances. The I ON/I OFF ratio is 2 × 109, 7 × 109, and 1 (Formula presented.) 10 for 5, 20, and 30 nm oxide thickness, respectively, as compared to 2 × 108 for the control sample. The interface–state–density is estimated to be 1.5 × 1013 cm−2 eV−1. I DS,sat is measured to be 710, 700, and 690 mA mm−1 for 5, 20, and 30 nm Ta2O5 thickness, respectively, compared to 725 mA mm−1 for the control sample. The presence of oxide does not change the other characteristics much.
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