Guoliang Ma

Research on the Combined Effects of Ionization and Displacement Defects in NPN Transistors Based on Deep Level Transient Spectroscopy

The properties of the combined effect between ionization and displacement defects have been researched on the base-collector junctions of 3DG110 silicon NPN bipolar junction transistors (BJTs) irradiated by 6 MeV carbon (C) ions with different fluence. The Gummel curve is used to characterize the degradation of the current gain at a given fluence. Nonlinear relationship, induced by 6 MeV C ions with lower fluence, between irradiation fluence and BJT radiation response can be observed, which is attributed to the combined effect. Evolution of deep level centers is characterized by the deep level transient spectroscopy (DLTS) with various biases. An unusual discovery is that the deep level centers decrease in the amplitude of DLTS peaks with increasing the biases. Based on the results of DLTS measurement, interface traps caused by 6 MeV C ions produce apparent enhanced effect to displacement defects in the base-collector junction of NPN BJT. Meanwhile, two factors, including bias used in DLTS measurement and irradiation fluence, can influence characteristics of DLTS signals caused by oxide-trapped charge. With increasing the bias or the irradiation fluence, both the height and the temperature of the defect peaks induced by the oxide charge in DLTS spectra will increase, illustrating concentration and energy level of the defects are enhanced.

Radiation Defects and Annealing Study on PNP Bipolar Junction Transistors Irradiated by 3-MeV Protons

A combined radiation effect is produced by 3-MeV protons, giving by both ionization and displacement damage, on semiconductor devices. In this paper, electrical characteristics and deep level transient spectroscopy (DLTS) are used to measure the radiation defects induced by ionization and displacement damage during the annealing process. A nonlinear relationship between the proton fluence and radiation response is clearly observed in the 3CG110 PNP bipolar junction transistor (BJT). DLTS analysis technique and annealing response of BJTs can provide important information on the nature of the ionization and displacement-induced defects, and measure them quantitatively, especially for the BJT with the combined radiation damage induced by protons. Based on the results of DLTS measurement and current gain annealing, the evolution of the ionization and displacement defects during the irradiation and annealing process is revealed, and the relationship between defects and current gain annealing is studied.

Synergistic Effect of Ionization and Displacement Defects in NPN Transistors Induced by 40-MeV Si Ion Irradiation With Low Fluence

Based on 3DG110 transistors and special gated NPN (GNPN) transistors, the characteristic of the synergistic effect between ionization and displacement defects induced by 40-MeV silicon (Si) ions with low fluence was investigated in terms of deep-level transient spectroscopy (DLTS). Nonlinear relationship, produced by the synergistic effect, between low fluence and radiation response can be obviously observed in the bipolar junction transistors (BJTs) under the exposure of 40-MeV Si ions. The DLTS signals of displacement defect centers and oxide-trapped charges are detected in the base-collector junction of the 3DG110 transistors. Meanwhile, based on the GNPN transistors, the DLTS signals of interface traps and displacement defects are measured in the base-collector junction. By comparison of the change in electrical parameters and the DLTS signals, it is found that the interface traps induce an enhanced effect to displacement defects in the base-collector junction of NPN BJT, whereas the oxide-trapped charge can suppress the DLTS signals of deep-level centers to a certain extent. Compared with the suppression action, the enhanced effect rising from ionization damage gives more contribution to the displacement damage. Moreover, the bias used during DLTS measurements can influence the characteristics of DLTS signals caused by oxide-trapped charge and interface traps. With increasing bias, both the height and temperature of ionization defect peaks in the DLTS spectra will increase, illustrating that concentration and energy level of these defects are raised.