Radiation damage of Ge-on-Si devices

Abstract

The radiation damage induced by 2-MeV electrons and 70-MeV protons in p +n diodes and p-channel MOS transistors, fabricated in epitaxial Ge-on-Si substrates is reported for the first time. For irradiation above 5×10 15 e/cm 2, it is noted that both the reverse and forward current increase, and that the forward current is lower after irradiation for a forward voltage larger than about 0.5 V. The reason for this might be an increased resistivity of the Ge-on-Si substrate. For p-MOSFETs, for a 1×10 16 e/cm 2 dose, a slight negative shift of the threshold voltage and a decrease of the drain current for input and output characteristics have been observed. In addition, g m decreases after irradiation. The degradation of the transistor performance is thought to be due to irradiation-induced positive charges in the high- κ gate dielectric. The induced lattice defects are also mainly responsible for the leakage current increase of the irradiated diodes.