Analysis of deep level defects in bipolar junction transistors irradiated by 2 MeV electrons.

In this work we investigate the deep level defects and the electrical characteristics of commercial PNP bipolar junction transistor (BJT) irradiated by 2MeV electrons with various fluences. The activation energy and the capture cross-section characteristics of the defects were obtained by deep level transient spectroscopy (DLTS). Five types of traps (including minority carrier traps and majority carrier traps) were observed before and after irradiation. By applying different reverse bias to the sample, the defects in the bulk and at the interface could be distinguished. The formation of such defects resulted in the degradation of the transistors-gain. Therefore the use of annealing methods at appropriate temperature was considered to recover the optimum electrical characteristics of the device.