# Mechanism of Synergistic Effects of Neutron- and Gamma-Ray-Radiated PNP Bipolar Transistors

## TL;DR

This paper investigates how neutron and gamma-ray radiation jointly affect PNP transistors, revealing complex synergistic damage mechanisms and defect passivation effects that can inform device resilience in space environments.

## Contribution

It introduces a new model explaining the synergistic effects and defect passivation in irradiated transistors, differing from previous models by including defect annihilation and passivation processes.

## Key findings

- Damage shows a 'tick'-like dependence on gamma dose after neutron irradiation.
- Two negative synergistic effects with similar magnitudes to ionization damage are identified.
- Gamma-ray-induced defect passivation can repair neutron-induced damage, enhancing device resilience.

## Abstract

The synergistic effects of neutron and gamma ray radiated PNP transistors are systematically investigated as functions of the neutron fluence, gamma ray dose, and dose rate. We find that the damages show a `tick'-like dependence on the gamma ray dose after the samples are radiated by neutrons. Two negative synergistic effects are derived, both of which have similar magnitudes as the ionization damage (ID) itself. The first one depends linearly on the gamma ray dose, whose slope depends quadratically on the initial displacement damage (DD) and can be attributed to the healing of neutron-radiation-induced defects in silicon. The second one has an exponential decay with the gamma ray dose, whose amplitude shows a rather strong enhanced low-dose-rate sensitivity (ELDRS) effect and can be attributed to the passivation of neutron-induced defects near the silica/silicon interface by the gamma-ray-generated protons in silica, which can penetrate the silica/silicon interface to passivate the neutron-induced defects in silicon. The simulated results based on the proposed model match the experimental data very well, but differ from previous model, which does not assume annihilation or passivation of the displacement defects. The unraveled defect annealing mechanism is important because it implies that displacement damages can be repaired by gamma ray radiation or proton diffusion, which can have important device applications in the space or other extreme environments.