Investigation of deep level defects in copper irradiated bipolar junction transistor K.V. Madhu a , Ravi Kumar b , M. Ravindra c , R. Damle a, * a Department of Physics, Jnanabharati, Bangalore University, Bangalore 560 056, India b Inter University Accelerator Center, Aruna Asaf Ali Marg, New Delhi 110 067, India c Components Division, ICG, ISRO Satellite Centre, Bangalore 560 017, India article info Article history: Received 13 September 2007 Received in revised form 29 May 2008 Accepted 4 June 2008 Available online 16 July 2008 The review of this paper was arranged by Prof. S. Cristoloveanu PACS: 71.55.i 72.20.Jv 78.70.g 61.82.Fk Keywords: Bipolar junction transistor Deep Level Transient Spectroscopy Deep level defects Shockley Read Hall recombination Isochronal annealing abstract Commercial bipolar junction transistor (2N 2219A, npn) irradiated with 150 MeV Cu 11+ -ions with fluence of the order 10 12 ions cm 2 , is studied for radiation induced gain degradation and deep level defects. I–V measurements are made to study the gain degradation as a function of ion fluence. The properties such as activation energy, trap concentration and capture cross-section of deep levels are studied by deep level transient spectroscopy (DLTS). Minority carrier trap levels with energies ranging from E C  0.164 eV to E C  0.695 eV are observed in the base–collector junction of the transistor. Majority carrier trap levels are also observed with energies ranging from E V + 0.203 eV to E V + 0.526 eV. The irradiated transistor is subjected to isothermal and isochronal annealing. The defects are seen to anneal above 350 °C. The defects generated in the base region of the transistor by displacement damage appear to be responsible for transistor gain degradation. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Bipolar junction transistors (BJTs) are still being extensively used in space and other radiation rich environments. These devices are sensitive to high energy particle irradiation. Considerable amount of data are available on the radiation effects of c-rays, fast neutrons, electrons and protons on semiconductor devices [1–5]. However, there appears to be rather little work on heavy ion in- duced effects and consequent characterization of defects by DLTS technique. Deep level defect monitoring plays an important role in designing a semiconductor device suitably for various applica- tions. Thus a study of radiation induced effects in semiconductor devices is important to observe changes in electrical characteristics and to get basic information regarding the generation and annihi- lation of defects. Exposure of semiconductor devices to high energy particle radi- ation is known to generate variety of defects. The nature of these defects generated by irradiation process depends on the properties of target as well as impinging high energy particle. To investigate these deep level defects several techniques are in practice. Deep le- vel transient spectroscopy (DLTS) is now an established technique for detecting and characterizing variety of defects in semiconduc- tor devices. DLTS is a high frequency capacitance transient thermal scanning method useful in observing a wide variety of traps in semiconductor devices [6]. The BJT used in the present study has been thoroughly studied in our earlier work for 24 MeV protons, 8 MeV electrons and 60 Co c-rays induced effects [7–9]. A DLTS study of deep level defects in Li-ion irradiated transistor (chosen from the same batch) is also reported earlier [10]. 2. Experimental details Commercial BJT (2N 2219A, npn) manufactured in an indige- nous technology from Continental Device India Ltd. (CDIL) has been selected for the present study. This device is a switching tran- sistor with standard configuration (base thickness is 2.0 lm and oxide thickness is 1.2 lm) suitable for low and high frequency 0038-1101/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.sse.2008.06.001 * Corresponding author. Tel.: +91 080 2296 1483; fax: +91 080 2321 9295. E-mail address: ramkrishnadamle@bub.ernet.in (R. Damle). Solid-State Electronics 52 (2008) 1237–1243 Contents lists available at ScienceDirect Solid-State Electronics journal homepage: www.elsevier.com/locate/sse