Investigation of Neutron Displacement Effects in Bipolar Amplifiers With Lateral and Substrate p-n-p Input Transistors

Neutron displacement effects in LM158L and LM158V bipolar amplifiers with lateral p-n-p (LPNP) and substrate p-n-p (SPNP) input transistors, respectively, were investigated based on neutron irradiation experiments and TCAD simulation. Experimental results suggest that the type of input transistor of the amplifier has great impact on the neutron displacement degradation. The input bias current and input offset current of the amplifier with SPNP input transistor increase more than that with LPNP input transistor, and more severe degradation in SPNP than that in LPNP leads to the corresponding more severe degradation in the specific amplifier. TCAD simulations were performed to analyze the physical mechanism of neutron displacement effects in these two kinds of input transistors. For LPNP, the hole current is much closer to the surface of the silicon, however for SPNP, the hole current is much deeper into the bulk silicon, so the displacement traps in whole bulk all contribute to the total recombination. Therefore, the total recombination in SPNP is larger than that in LPNP, resulting in more severe degradation under neutron irradiation.