Evolution of Deep Level Centers in NPN Transistors Following 35 MeV Si Ion Irradiations With High Fluence

The properties of deep level centers have been researched on the base-collector junctions of 3DG110 silicon NPN bipolar junction transistors (BJTs) irradiated by 35 MeV silicon (Si) ions with different fluence. The Gummel curve is utilized to characterize the degradation of current gain at a given fluence. 35 MeV Si ions with high fluence can induce high levels of damage on current gain of 3DG110 BJTs, the value of which could be less than 1. Evolution of deep level centers, induced by such high fluence in NPN BJTs, is characterized by the deep level transient spectroscopy (DLTS). SRIM software is employed to estimate the number of vacancies produced by 35 MeV Si ions and to calculate the Si ion end of range in BJTs. Based on the calculations by SRIM and measurements by DLTS, when the irradiation fluence is high enough, 35 MeV Si ions with the end of range deeper than the DLTS-probed depths, can also produce apparent defect clusters, which is similar to those with the end of range in DLTS-probed depths. These irradiation-induced defect clusters can suppress the V₂(=/-) DLTS signature. Especially, compared to shallower deep levels, the deeper levels, such as V₂(-/0) centers, are the critical defects to degrade the current gain.