Effects of Applied Bias and High Field Stress on the Radiation Response of GaN/AlGaN HEMTs

Abstract

The sensitivity of GaN/AlGaN HEMTs to 1.8 MeV proton irradiation is greatly enhanced by biasing the devices during irradiation and/or applying high field stress before irradiation. The resulting defect energy distributions are evaluated after irradiation and/or high field stress via low-frequency noise measurements. Significant increases are observed in acceptor densities for defects with <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim $</tex></formula> 0.2 and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sim $</tex> </formula> 0.7 eV energy levels. These defects appear to dominate the degradation in threshold voltage and transconductance for these devices. Density functional theory (DFT) calculations show that N vacancy-related defects in GaN and hydrogenated O <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${_{\rm N}}$</tex></formula> complexes in AlGaN are strong candidates for the defects with <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\sim $</tex></formula> 0.2 eV energy levels in these devices. We also present evidence that the previously unidentified <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\sim} $</tex></formula> 0.7 eV defect in GaN is a N anti-site defect (N <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$_{\rm Ga}$</tex></formula> ).