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Performance Improvement in AlGaN/GaN High-Electron-Mobility Transistors by Low-Temperature Inductively Coupled Plasma–Chemical Vapor Deposited SiN<inf>x</inf> as Gate Dielectric and Surface Passivation
Journal
Physica Status Solidi (A) Applications and Materials Science
ISSN
18626300
Date Issued
2022-12-01
Author(s)
Surana, Vivek Kumar
Ganguly, Swaroop
Saha, Dipankar
Abstract
This work demonstrates performance improvements in AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) using low-temperature inductively coupled plasma chemical vapor deposited (ICP–CVD) silicon nitride (SiNx). The low-temperature SiNx is used for both device passivation and gate dielectric. The bandgap of SiNx (4.9 eV) and AlGaN/SiNx type-II staggered band alignment (ΔEc = 1.4 eV) are determined using ultraviolet-visible spectroscopy and ultraviolet photoelectron spectroscopy, respectively. The SiNx layer effectively increases the in-plane tensile strain in the AlGaN barrier layer. The tensile strain increases by 0.08% for a 150 nm SiNx layer. The corresponding increase in the piezoelectric polarization and 2D electron gas (2DEG) density is 1.5 × 1012 and 1.44 × 1012 cm−2, respectively. The transistor's on-resistance decreases to 9.33 Ω mm compared with 14 Ω mm measured for the control devices with gate length 1 μm and source and drain separation of 11 μm. The gate leakage current reduces by more than three orders of magnitude. The ION/IOFF ratio increases by two orders of magnitude. The improvements in the physical and electrical properties of the low-temperature-deposited ICP–CVD SiNx MIS-HEMTs make it a viable candidate for low-thermal-budget fabrication. This nitride can be used with non-alloyed Ohmic contacts on GaN for extremely low-thermal-budget transistors.
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