The Effect of Ionization Damage on Displacement Damage in AlGaN/GaN HEMTs

Abstract

This article investigates the synergistic radiation effects on AlGaN/GaN high electron mobility transistors (HEMTs) using the individual irradiation of 1-MeV electrons and 170-keV protons, and the combined irradiation of 170-keV electrons and 170-keV protons. The electrical degradation of HEMTs is examined under the individual irradiation and the combined irradiation. The transconductance and threshold voltage were almost unchanged when the fluence of 1-MeV electron irradiation reached <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\times 10^{14}$ </tex-math></inline-formula> cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-2}$ </tex-math></inline-formula> . The AlGaN/GaN HEMTs show excellent resistance to ionization radiation. It shows a positive shift of threshold voltage after proton irradiation reached <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\times 10^{13}$ </tex-math></inline-formula> cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-2}$ </tex-math></inline-formula> . The drain current and the carrier mobility obviously decrease under proton irradiation. The negatively charged displacement defects deplete and scatter the channel carriers, leading to the degradation of the samples. The displacement damage is also the main reason during combined irradiation. However, with the participation of electron irradiation, the degradation of the transistors is much greater than that caused by individual proton irradiation. The degradation rate caused by the combined irradiation is almost three times that caused by the individual proton irradiation. In AlGaN/GaN HEMTs, there is a synergistic effect between ionization and displacement effect. This means that ionization radiation can promote displacement damage.