Further Exploration in Displacement Damage Correlation of Neutrons and Si Ions in VPNP BJTs

Abstract

This study systematically examines the equivalence of displacement radiation damage in vertical p-n-p (VPNP) bipolar transistors between 1-MeV neutron-equivalent and multi-energy silicon ion irradiation environments through the development of an enhanced non-ionizing energy loss (NIEL) calculation methodology. A comparative irradiation study was performed on identical VPNP bipolar transistors from the same production batch, employing both neutron irradiation and silicon ion bombardment at varying energy levels. Depth-dependent NIEL distributions were numerically simulated for both radiation species, enabling precise extraction of total non-ionizing dose (TNID) deposition in the base region per unit fluence. Analysis of radiation-induced electrical degradation demonstrates that the inverse current gain variation in bipolar transistors exhibits approximate adherence to the Messenger-Spratt equation when correlated with TNID. However, the NIEL methodology fails to establish a direct displacement damage correlation between different particle species. Comparative deep-level transient spectroscopy (DLTS) characterizations following neutron and 30-MeV silicon ion irradiation reveal three identical defect types induced by both radiation sources while demonstrating significant ionization damage interference in displacement defect formation during 30-MeV silicon irradiation. Notably, the refined NIEL methodology achieves remarkable consistency in correlating silicon ion and neutron radiation damage data, with linear fitting analysis yielding Pearson correlation coefficients exceeding 0.99. This validation confirms the improved predictive capability of the proposed NIEL framework for multi-particle radiation damage equivalence assessment.