Millimeter wave photoresponse of low-dose radiation damaged silicon

This paper is about analyzing millimeter wave probe signal (150 GHz) differential absorption datasets to reveal some changed transmission and reflection properties of 500 µm p-doped Si wafers exposed to 1.2, 2.0, and 0.75 MeV gamma, proton, and chlorine ion beams (with doses in range 0.1 to 6 MGy). The decay portion of the respective pristine and irradiated sample RF responses were tri-exponentially fitted, and respective time constants evaluated as function of radiation dose. The peak RF voltages and their ratio with the transmitted DC voltages at each of the 532 nm laser radiation fluence points were plotted as function of laser radiation itself. Radiation dose is found to enhance the third time constant τ3 that decays very fast beyond 0.1 MGy. Average τ for all irradiated samples correlates negatively with radiation dose (R = −0.83). 4-probe resistivity of 2 MeV H+ exposed samples increase ~10x and enhances the peak RF voltage to DC voltage ratio (ΔVT/Vdc). Chlorine (Cl2+) irradiated Si wafers show feeble ΔVT/Vdc compared to those exposed with γ or H+ beam. DC transmittances of all samples at 150 GHz lie in the range 0.46–0.64.