High-energy electron induced gain degradation in bipolar junction transistors S.R. Kulkarni a,1 , M. Ravindra b , G.R. Joshi b , R. Damle c, * a Department of PG Studies in Physics, SBMJC, Jayanagar, Bangalore 560 011, India b Components Division, ICG, ISRO Satellite Centre, Airport Road, Bangalore 560 017, India c Department of Physics, Bangalore University, Bangalore 560 056, India Received 15 November 2005; received in revised form 27 May 2006 Available online 10 July 2006 Abstract This paper describes the effect of 8 MeV electron beam on the forward current gain of space borne commercial indigenous bipolar junction transistors 2N2219A (npn), 2N3019 (npn) and 2N2905A (pnp). The devices are exposed to 8 MeV electron in the biased con- dition. The collector characteristics and Gummel plots are obtained as a function of accumulated dose. An excess base current model as well as Messenger–Spratt equation have been used to account for the observed gain degradation. The results indicate that 8 MeV elec- trons of high dose rate induce gain degradation by increasing the base current as well as decrease in collector current. The current gain degradation appears to be predominantly due to displacement damage in the bulk of the transistor. Off-line measurements of the h FE of the irradiated transistors indicate that the displacement induced defect and recombination centers do not anneal even at 150 °C. Ó 2006 Elsevier B.V. All rights reserved. PACS: 61.82.Fk Keywords: High-energy electron irradiation; Gain degradation; Excess base current; BJT; Thermal annealing 1. Introduction The study of radiation-induced effects in semiconductor devices, in general, is important both from the basic as well as applied point of view. From the basic point of view, it is important to have a broader understanding of the damage process. From the applied point of view, it is important to assess the device performance when they need to be oper- ated in radiation environment. A number of non-radhard versions of the devices from international vendors have been characterized for radiation-induced effects for use in space applications. However, several semiconductor devices, which are not available in radhard versions, are still being used in spacecraft systems. In the recent years, there is an increasing need for some space agencies to employ indigenously made devices for space applications. As a result, it is essential to characterize these for radiation induced effects and qualify the parts for use in spacecraft systems. Discrete BJTs are still employed for space applications due to their current drive capability, linearity and excellent matching characteristics. One of the important aspect of the characterization of BJTs for radiation-induced effects is the radiation-induced gain degradation. The BJTs are particularly found to be vulnerable to ionizing radiation and transistor gain degradation is the primary cause for parametric shifts and functional failures. Although there are several studies looking into the mechanism of gain deg- radation in BJTs subjected to radiation, a widely accepted model accounting for the same has not emerged. The deg- radation of the forward current gain in the bipolar junction transistor when exposed to radiation is dependent on many factors including the nature of radiation particulate and 0168-583X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2006.05.028 * Corresponding author. E-mail addresses: srinivask24@hotmail.com (S.R. Kulkarni), damler- aju@yahoo.com (R. Damle). 1 Tel.: +91 9448923982; fax: +91 80 51210692. www.elsevier.com/locate/nimb Nuclear Instruments and Methods in Physics Research B 251 (2006) 157–162 NIM B Beam Interactions with Materials & Atoms