N. Pushpa

JSS Medical College, Mysore, Mahisūr, Karnātaka, India

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Publications (16)10.87 Total impact

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    ABSTRACT: The effects of 3 MeV proton irradiation on the I-V characteristics of NPN rf power transistors were studied in the dose range of 100 Krad to 100 Mrad. The different electrical characteristics like Gummel, current gain and output characteristics were systematically studied before and after irradiation. The recovery in the I-V characteristics of irradiated NPN BJTs were studied by isochronal and isothermal annealing methods.
    03/2014; 1591(1).
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    ABSTRACT: First-generation (50 GHz) silicon–germanium heterojunction bipolar transistors (SiGe HBT) were irradiated with 75 MeV boron ions and 100 MeV oxygen ions. The aim of the present investigation is to study the degradation of current–voltage (I–V) characteristics due to different linear energy transfer ions. The in situ I–V characteristics were measured before and after ion irradiation are forward mode and inverse mode Gummel characteristics, excess base current and current gain. It was found that the oxygen ion-irradiated SiGe HBT showed slightly more degradation when compared with boron ion-irradiated devices. The damage constant was calculated using the Messenger–Spratt equation, which confirmed more degradation in the case of oxygen ion-irradiated HBTs.
    Radiation Effects and Defects in Solids 08/2013; 168. · 0.50 Impact Factor
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    ABSTRACT: The third generation Silicon-Germanium Heterojunction Bipolar Transistors (200 GHz SiGe HBTs) were irradiated with 50 MeV Lithium and 75 MeV Boron ions in the dose ranging from 1 Mrad to 100 Mrad. The different electrical characteristics like forward-mode Gummel characteristics, inverse-mode Gummel characteristics, excess base current and current gain were studied before and after ion irradiation. The damage constants for 50 MeV Li3+ and 100 MeV B5+ ion irradiated SiGe HBTs were calculated using Messenger-Spratt equation.
    02/2013;
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    ABSTRACT: In this study NPN rf power transistors were irradiated by 175 MeV Ni13+ ions in the dose range of 100 krad to 100 Mrad. Their characteristics such as excess base current (ΔIB = IBpost − IBpre), dc current gain (hFE), transconductance (gm) and collector-saturation current (ICSat) were studied before and after irradiation. The damage factor (K) for hFE was calculated using Messenger–Spratt relation. The base current (IB) was found to increase significantly after irradiation and in turn decreases the hFE. The gm and collector current (IC) in the saturation region (ICSat) were found to decrease with increase in radiation dose. The results obtained here were also compared with that obtained by 140 MeV Si10+ ions, 100 MeV F8+ ions, 95 MeV O7+ ions and 50 MeV Li3+ ions irradiation studies in the same dose ranges to understand the LET effects. The recovery in the I–V characteristics of irradiated NPN transistors were studied by isothermal and isochronal annealing methods.
    Current Applied Physics 01/2013; 13(1):66-75. · 2.03 Impact Factor
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    ABSTRACT: In this paper we present the comprehensive results on the effects of different radiation on the electrical characteristics of different semiconductor devices like Si BJT, n-channel MOSFETs, 50 GHz and 200 GHz silicon-germanium heterojunction bipolar transistor (SiGe HBTs). The total dose effects of different radiation are compared in the same total dose ranging from 100 krad to 100 Mrad. We show that the irradiation time needed to reach very high total dose can be reduced by using Pelletron accelerator facilities instead of conventional irradiation facilities.
    AIP Conference Proceedings. 06/2012; 1447(1).
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    ABSTRACT: N-channel depletion metal oxide semiconductor field effect transistors (MOSFETs) were irradiated with 175 MeV Ni3+ ions and Co-60 gamma radiation in the dose range of 100 krad to 100 Mrad. The I-V characteristics of MOSFETs were studied systematically before and after ion and gamma irradiation. The threshold voltage (VTH) of the irradiated MOSFETs was found to decrease with increase in ion and gamma dose. The more degradation was observed in the devices irradiated with Co-60 gamma radiation than irradiated with Ni13+ ions at given total doses.
    06/2012;
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    ABSTRACT: The dc characteristics of NPN rf power transistors were studied systematically before and after irradiation by 50 MeV Li3+ ions, 100 MeV F8+ ions and 140 MeV Si10+ ions in the dose range of 100 krad to 100 Mrad. The transistor parameters such as excess base current (ΔIB = IBpost-IBpre), dc current gain (hFE), and collector-saturation current (ICSat) were determined before and after irradiation. The base current (IB) was found to increase significantly after ion irradiation and this in turn decreases the hFE of the transistors. Further, the output characteristics of the irradiated devices exhibit the decrease in the collector current at the saturation region (ICSat) with increase of ion dose.
    07/2011;
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    ABSTRACT: Third generation advanced Silicon-Germanium Heterojunction Bipolar Transistors (200 GHz SiGe HBTs) were exposed to different radiations like 50 MeV lithium ions, 63 MeV proton and Co-60 gamma radiation in the dose range of 300 krad to 10 Mrad. The DC electrical characteristics like forward mode Gummel characteristics, inverse mode Gummel characteristics, excess base current, current gain, neutral base recombination, avalanche multiplication and output characteristics were measured before and after irradiation for three different radiations and the results are compared in this paper. The results show that the Li + ions impart more energy and create significant amount of damage in the surface and bulk of the transistor when compared to gamma and proton irradiation.
    Journal of Nano- and Electronic Physics. 01/2011; 3:348.
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    ABSTRACT: The total dose effects of 50 MeV lithium (Li3+) ions on 200 GHz (8HP) silicon–germanium heterojunction bipolar transistors (SiGe HBTs) are studied in total doses ranging from 300 krad to 10 Mrad. The different electrical characteristics, such as the Gummel characteristics, dc current gain (h FE), neutral base recombination, avalanche multiplication of carriers (M−1) and output characteristics (I C–V CE), were studied before and after Li3+ ion irradiation. The results of 50 MeV Li3+ ion irradiation on SiGe HBTs are compared with 60Co gamma irradiation results in the same dose ranges.
    Radiation Effects and Defects in Solids 01/2011; 166:710-717. · 0.50 Impact Factor
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    ABSTRACT: N-channel depletion MOSFETs were irradiated with 140 MeV Si10+ ions, 100 MeV F8+ ions and 48 MeV Li3+ ions in the dose range from 100 krad to 100 Mrad. The MOSFET parameters such as threshold voltage (VTH), transconductance (gm) and mobility of carriers (μ) were determined by systematically studying the I–V characteristics before and after irradiation. The ion irradiated results were compared with Co-60 gamma irradiated results in the same dose range. The degradation in VTH, gm and μ was found to be more for the devices irradiated with Co-60 gamma radiation than that irradiated with swift heavy ions.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2011; · 1.19 Impact Factor
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    ABSTRACT: NPN RF power transistors were irradiated with 140 MeV Si10+ ions, 100 MeV F8+ ions, 50 MeV Li3+ ions and Co-60 gamma radiation in the dose range from 100 krad to 100 Mrad. The transistor characteristics are studied before and after irradiation from which the parameters such as Gummel characteristics, excess base current (ΔIB = IBpost − IBpre), dc current gain (hFE), transconductance (gm) and collector-saturation current (ICSat) are determined. The degradation observed in the electrical characteristics is almost the same for different types of ion irradiated NPN RF power transistors with similar total doses although there is a large difference in the linear energy transfer (LET) of the ions. Further, it was observed more degradation in DC I–V characteristics of ion irradiated devices than the Co-60 gamma irradiated devices for higher doses.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2011; · 1.19 Impact Factor
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    ABSTRACT: We have investigated the effects of 50 MeV lithium ion irradiation on the DC electrical characteristics of first-generation silicon–germanium heterojunction bipolar transistors (50 GHz SiGe HBTs) in the dose range of 600 krad to 100 Mrad. The results of 50 MeV Li3+ ion irradiation on the SiGe HBTs are compared with 63 MeV proton and Co-60 gamma irradiation results in the same dose range in order to understand the damage induced by different LET species. The radiation response of emitter–base (EB) spacer oxide and shallow trench isolation (STI) oxide to different irradiation types are discussed in this paper. We have also focused on the efficacy in the application of a Pelletron accelerator to study total dose irradiation studies in SiGe HBTs.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2011; · 1.19 Impact Factor
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    ABSTRACT: Third generation 200 GHz silicon–germanium Heterojunction Bipolar Transistors (Si–Ge HBTs) were irradiated with high dose Co-60 gamma radiation up to 100 Mrad. Pre-radiation and post-radiation DC figures of merits were used to quantify the radiation tolerance of the different geometry devices. The different electrical characteristics like Gummel measurements, excess base current, current gain, transconductance, neutral base recombination, avalanche multiplication of carriers and output characteristics were studied for different doses from 100 krad to 100 Mrad of total doses. The Si–Ge HBTs showed robust ionizing radiation tolerance up to a total dose of 100 Mrad.
    Solid-State Electronics 12/2010; 54:1554. · 1.48 Impact Factor
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    ABSTRACT: N-channel MOSFETs were irradiated by 48MeV Li3+ ions, 100MeV F8+ ions and Co-60 gamma radiation with doses ranging from 100krad to 100Mrad. The threshold voltage (VTH), voltage shift due to interface trapped charge (ΔVNit), voltage shift due to oxide trapped charge (ΔVNot), density of interface trapped charge (ΔNit), density of oxide trapped charge (ΔNot), transconductance (gm), mobility (μ) of electrons in the channel and drain saturation current (ID Sat) were studied as a function of dose. Considerable increase in ΔNit and ΔNot, and decrease in VTH, gm and ID Sat were observed in all the irradiated devices. We correlated the degradation of μ with the ΔNit and the effect of ΔNot is found to be negligible for degrading the μ. The maximum degradation was observed for the devices irradiated with Co-60 gamma radiation when compared with those irradiated with ions, since gamma radiation can generate more trapped charge in field oxide when compared to the high energy ions.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2010; 613(2):280-289. · 1.14 Impact Factor
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    ABSTRACT: The dc characteristics exhibited by NPN power transistors are studied systematically before and after irradiation by 100 MeV F8+ ions and 50 MeV Li3+ ions in the dose range of 100 krad to 100 Mrad. The transistor parameters such as excess base current (ΔIB=IBpost–IBpre), dc current gain (hFE), transconductance (gm), and collector-saturation current (ICsat) were studied before and after irradiation. The damage factors (k) for hFE were calculated for ion irradiated transistors using Messenger–Spratt relation. The base current (IB) was found to increase significantly after ion irradiation and this in turn decreases the hFE of the transistors. The gm decreases significantly after ion irradiation. Moreover, the output characteristics of irradiated devices also show that the collector current (IC) in the saturation region (ICsat) decrease with increase in ion dose. The observed change in these characteristics may be due to the ion induced generation–recombination (G–R) centers in emitter-base (E-B) spacer oxide and the ion induced point defects and their complexes in the transistor structure.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2010; 620:450-455. · 1.14 Impact Factor
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    ABSTRACT: Abstract The effects of 8 MeV electrons and 60 and 95 MeV oxygen ions on the electrical properties of Si npn RF power transistors have been investigated as a function of fluence. The dc current gain (h FE), displacement damage factor, excess base current (Δ I B=I Bpost−I Bpre), excess collector current (Δ I C=I Cpost−I Cpre), collector saturation current (I CS) and deep level transient spectroscopy trap signatures of the irradiated transistors were systematically evaluated.
    Radiation Effects and Defects in Solids 01/2009; 164(10):592-603. · 0.50 Impact Factor

Publication Stats

11 Citations
10.87 Total Impact Points

Institutions

  • 2014
    • JSS Medical College, Mysore
      Mahisūr, Karnātaka, India
  • 2009–2013
    • University of Mysore
      • Department of Physics
      Mahisūr, Karnātaka, India
  • 2010
    • Pondicherry University
      • Department of Physics
      Pondicherry, Union Territory of Puducherry, India