2020 journal article

Engineering a Unified Dielectric Solution for AlGaN/GaN MOS-HFET Gate and Access Regions

IEEE TRANSACTIONS ON ELECTRON DEVICES, 67(3), 881–887.

By: F. Azam n, A. Tanneeru n , B. Lee n & V. Misra n 

co-author countries: United States of America πŸ‡ΊπŸ‡Έ
author keywords: AlGaN/GaN; atomic layer deposition (ALD); current collapse; HfO2; high electron mobility transistor (HEMT); high-k; high-temperature reverse bias (HTRB); hydroxyl; interface; MOS; HFET; oxidant; reliability; traps
Source: Web Of Science
Added: April 14, 2020

Typically GaN metal-oxide-semiconductor heterojunction-field-effect transistors (MOS-HFETs) have used two separate dielectrics for the gate and access regions. However, as this article shows, with proper gate-stack engineering, a unified dielectric solution can be achieved for the transistor. HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> dielectrics were deposited by atomic layer deposition (ALD). Two types of oxidants were investigated, namely, water (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O) and ozone (O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ). It was found that MOS-HFETs with O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> oxidant yielded lower threshold voltage (VTH) shifts, higher maximum drain current (IDS,max) of 340 mA/mm, 20% lower ON-resistance (RON), higher peak transconductance at 112.66 mS/mm, lower hysteresis, and lower gate leakage (5.4 Γ— 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) compared to water oxidant based MOS-HFETs with IDS,max of 240 mA/mm, 81.38 mS/mm peak transconductance, and 1.7 Γ— 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> gate leakage. DC/RF dispersion tests showed MOS-HFETs with O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> oxidant had -200x better current collapse recovery. Temperature characterization and reliability test results, such as high-temperature reverse bias (HTRB), are published for the first time on ALD-HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /AlGaN/GaN MOSHFETs using tetrakis(dimethylamino)hafnium (TDMAH) and O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> precursor. Using an ozone oxidant provided more stability (i.e., less variability in RON and VTH) as a function of temperature. Finally, when devices were electrically stressed in the OFF-state, the HTRB test showed minimal VTH drift (<; 0.5 V) in the case of O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> oxidant versus much larger VTH drift (2.5 V) in the case of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O oxidant.