Trap Thawing-Induced Threshold Voltage Instability in p-GaN HEMTs at Cryogenic Temperatures During Pre-Stress

In this paper, the pre-stress in p-GaN high-electron-mobility transistors (HEMTs) at cryogenic temperatures is investigated, revealing the trap thaw-out effect: the frozen hole traps acquire energy from high-energy electrons, leading to their thawing and causing a positive threshold voltage (V<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub>) shift. The pre-stress activates additional hole traps, contributing to the gate leakage current (I<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GSS</sub>) induced by Poole-Frenkel (PF) emission. The analyses of I<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GSS</sub>, capacitance deep-level transient spectroscopy (C-DLTS), and TCAD simulation are conducted to identify the underlying mechanisms. Our findings refine the overall behavior of traps at cryogenic temperatures, providing a more comprehensive understanding of p-GaN HEMTs reliability for wide cryogenic applications, such as superconducting systems and space electronics.