A. P. Gnana Prakash

An investigation of electron and oxygen ion damage in Si npn RF power transistors

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.

50 MeV Li3+ ion irradiation effects on advanced 200 GHz SiGe HBTs

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.

The effect of 63 MeV hydrogen ion irradiation on 65 GHz UHV/CVD SiGe HBT BiCMOS technology

Two thousand arrays of second generation (6HP) silicon–germanium heterojunction bipolar transistors (SiGe HBTs) were exposed to 63 MeV hydrogen ions at a fluence ranging from 1×1012 to 5×1013 cm−2. The dc electrical measurements, such as Gummel characteristics, excess base current (Δ I B=I Bpost−I Bpre), current gain (h FE), neutral base recombination, avalanche multiplication factor (M−1) and output characteristics (V CE–I C), were systematically studied before and after hydrogen ion irradiation. The SiGe HBT showed 80% degradation in forward-mode dc current gain after a total dose of 5×1013 cm−2 hydrogen ion irradiation.

In situ investigation of 75 MeV boron and 100 MeV oxygen ion irradiation effects on 50 GHz silicon–germanium heterojunction bipolar transistors

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.

MLO: Multi-level Optimization to Enhance the Network Lifetime in Large Scale WSN

Ensuring the optimal energy efficiency is one of the unsolved problems in Wireless Sensor Networks (WSN) owing to varying power requirements of hardware components of sensors, massive load on data aggregation and less efficient energy aware routing policies. Hence, this paper describes a multi-level optimization (MLO) for the purpose of enhancing the network lifetime in WSN. The techniques discussed in this paper uses graph theory for formulating data aggregation and uses first order radio-energy model for evolving up with novel routing condition to attain less depletion of energy while performing data aggregation. The outcome of the study was compared with standard LEACH algorithm with respect to energy consumption and time to find MLO is better than LEACH.

A comparison of 75 MeV boron and 50 MeV lithium ion irradiation effects on 200 GHz SiGe HBTs

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.

MeMLO: Mobility-Enabled Multi-level Optimization Sensor Network

The paper presents a technique called as Mobility-Enabled Multi Level Optimization (MeMLO) that addressing the existing problem of clustering in wireless sensor net-work (WSN). The technique enables selection of aggregator node based on multiple optimization attribute which gives better decision capability to the clustering mechanism by choosing the best aggregator node. The outcome of the study shows MeMLO is highly capable of minimizing the halt time of mobile node that significantly lowers the transmit power of aggregator node. The simulation outcome shows negligible computational complexity, faster response time, and highly energy efficient for large scale WSN for longer simulation rounds as compared to conventional LEACH algorithm.

Comparison of 1 MeV electron, Co-60 gamma and 1 MeV proton irradiation effects on silicon NPN transistors

ABSTRACT The total dose effects of 1 MeV electrons on the dc electrical characteristics of silicon NPN transistors are investigated in the dose range from 100 krad to 100 Mrad. The different electrical characteristics such as Gummel characteristics, excess base current (ΔIB), dc current gain (hFE), transconductance (gm), displacement damage factor (K) and output characteristics were studied in situ as a function of total dose. A considerable increase in base current (IB) and a decrease in hFE, gm and ICSat was observed after 1 MeV electron irradiation. The collector–base (C–B) junction capacitance of transistors was measured to estimate the change in the effective carrier concentration. After 1 MeV electron irradiation, a considerable degradation in capacitance was observed. The plot of (1/C2) versus voltage shows that the effective carrier concentration and built-in voltage (Vbi) increase marginally upon 1 MeV electron irradiation. The results of 1 MeV electron irradiation were compared with 1 MeV proton and Co-60 gamma irradiation results in the same dose range. The degradation for 1 MeV electron and Co-60 gamma-irradiated transistors was significantly less when compared to 1 MeV proton-irradiated transistor. The 1 MeV proton, 1 MeV electron and Co-60 gamma-irradiated transistors were subjected to isochronal annealing to analyze the recovery of the electrical parameters.

A comparison of 100 MeV oxygen ion and Co-60 gamma irradiation effect on 200 GHz SiGe HBTs (HF 12)

We have investigated the total dose effects of 100 MeV Oxygen ion irradiation on the dc electrical characteristics of Silicon-Germanium Heterojunction Bipolar Transistors (SiGe HBTs). The results of oxygen ion irradiation were compared with Co-60 gamma irradiation in the same total dose range (1 Mrad to 100 Mrad). The results show that even after 100 Mrad of total dose, the degradation in the electrical characteristics of SiGe HBT is acceptable from the circuit design point of view.

Electrical Properties of Nano Zinc Ferrites Prepared by Solution Combustion and Hydrothermal Methods

Zinc Ferrite (ZF) nanopowders relatively uniform size distributions ranging from 5 to 14 nm were prepared by solution combustion and hydrothermal methods. The PXRD showed cubic phase, spinel structure, and particle size in nanoscale. The SEM images confirm the agglomeration of the product composed of uniform nanoparticles of flakes type and spherical type in combustion and hydrothermal methods respectively. The purity check was done by FTIR. The optical band gap energy (Eg) obtained by UV-Vis spectra of the ZF nanopowders prepared by solution combustion and hydrothermal methods were found to be 1.985 eV and 1.99 eV respectively. The present study clearly shows that the distribution of the cations within the spinel lattice of the ferrite nanoparticles are strongly affected by the synthesis method used. Results suggest that the electrical properties depend on the particular method of preparation and sintering temperature of the prepared samples. The resistivity of the samples increased to the order of 103 by sintering the samples. It is observed that the activation energy (Ea) decreases with increasing the sintering temperature.