Abstract

The influence of 100 MeV Silicon (Si) ion irradiation on electrical characteristics of Si photo detectors has been analyzed using in-situ current-voltage characterization (I-V) in dark condition. The irradiation was performed over a wide range of fluences from 1×10¹¹ ions/cm² to 1×10¹³ ions/cm². Key electrical parameters such as ideality factor (n), series resistance (R_s) and reverse bias leakage current (I_R) for each irradiation fluence have been extracted from the I-V characteristics. The ideality factor of the unirradiated detector is found to be 1.48 and it gradually increased up to the fluence of 5×10¹¹ ions/cm², then it saturates around 3.4-3.5 for higher fluences. The I-V characteristics showed significant increase in forward bias and drastic increase in reverse leakage current. The value of I_R is   7.23 nA for unirradiated detector and it increases about four orders of magnitude up to 5×10¹¹ ions/cm². Further there is no observable change in the value of I_R. However the value of R_s increases initially and slightly decrease at higher fluences. The observed results are interpreted in terms of energy loss mechanisms of swift heavy ion as it passes through the different layers of the detector. The radiation induced defects in the bulk region and activation of multiple current transport mechanisms have attributed to the observed deviations in the electrical behaviour of the device. SRIM (Stopping power and Range of Ion in Matter) and TRIM (Transport and Range of Ion in Matter) simulation results of damage induced in the device have been reported in the present study. Linear energy transfer (LET), non ionizing energy loss (NIEL) damage contributions, total ionization dose (TID) and displacement damage dose (D_d) has been correlated with the observed degradation. Quantitative estimation of radiation hardness of the Si photo detector is done by comparing with the equivalent damage created by the proton at similar penetration depth in the present device structure.

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