Displacement Damage in an Irradiated 4H-SiC MESFET

Radiation-induced degradation of a commercial 4H-SiC metal-semiconductor field-effect transistor (MESFET) is examined following exposure to 941-MeV Bi ions, 20-MeV protons and 60Co <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula>-rays. The degradation results primarily from displacement damage. The device is radiation-hard to an equivalent 1-MeV neutron fluence of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.6\times 10^{14}$ </tex-math></inline-formula> cm−2. The relative contributions of carrier removal and mobility degradation to device degradation are comparable. The channel mobility is reduced by 40% at a non-ionizing dose (NID) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.1\times 10^{12}$ </tex-math></inline-formula> MeV/g. The carrier removal rate normalized to 1-MeV neutron fluence is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$32~\pm ~3$ </tex-math></inline-formula> cm−1, which is more than six times the rates reported for similar 6H-SiC devices. The difference in carrier removal rates for the two polytypes is apparently related to differences in radiation defect properties. The degradation scales with elastic non-ionizing energy loss (NIEL), which suggests that nuclear inelastic interactions, which tend to produce long recoils relative to the device channel depth, do not contribute to parametric degradation. This implies that qualification testing of certain device types with high-energy protons directed at the device surface may lead to an overestimation of device lifetime in space.