Simulation of 4H-SiC MESFET for High Power and High Frequency Response

S. N. Chattopadhyay,P. Pandey,C. B. Overton,S. Krishnamoorthy,S.K. Leong 대한전자공학회 2008 Journal of semiconductor technology and science Vol.8 No.3

In this paper, we report an analytical modeling and 2-D Synopsys Sentaurus TCAD simulation of ion implanted silicon carbide MESFETs. The model has been developed to obtain the threshold voltage, drain-source current, intrinsic parameters such as, gate capacitance, drain-source resistance and transconductance considering different fabrication parameters such as ion dose, ion energy, ion range and annealing effect parameters. The model is useful in determining the ion implantation fabrication parameters from the optimization of the active implanted channel thickness for different ion doses resulting in the desired pinch off voltage needed for high drain current and high breakdown voltage. The drain current of approximately 10 A obtained from the analytical model agrees well with that of the Synopsys Sentaurus TCAD simulation and the breakdown voltage approximately 85 V obtained from the TCAD simulation agrees well with published experimental results. The gate-to-source capacitance and gate-todrain capacitance, drain-source resistance and transconductance were studied to understand the device frequency response. Cut off and maximum frequencies of approximately 10 ㎓ and 29 ㎓ respectively were obtained from Sentaurus TCAD and verified by the Smith’s chart.

Optically Controlled Silicon MESFET Modeling Considering Diffusion Process

S. N. Chattopadhyay,N. Motoyama,A. Rudra,A. Sharma,S. Sriram,C. B. Overton,P. Pandey 대한전자공학회 2007 Journal of semiconductor technology and science Vol.7 No.3

An analytical model is proposed for an optically controlled Metal Semiconductor Field Effect Transistor (MESFET), known as Optical Field Effect Transistor (OPFET) considering the diffusion fabrication process. The electrical parameters such as threshold voltage, drain-source current, gate capacitances and switching response have been determined for the dark and various illuminated conditions. The Photovoltaic effect due to photogenerated carriers under illumination is shown to modulate the channel cross-section, which in turn significantly changes the threshold voltage, drainsource current, the gate capacitances and the device switching speed. The threshold voltage VT is reduced under optical illumination condition, which leads the device to change the device property from enhancement mode to depletion mode depending on photon impurity flux density. The resulting I-V characteristics show that the drain-source current IDS for different gate-source voltage Vgs is significantly increased with optical illumination for photon flux densities of Φ = 10<SUP>15</SUP> and 10<SUP>17</SUP> /㎠s compared to the dark condition. Further more, the drain-source current as a function of drain-source voltage VDS is evaluated to find the I-V characteristics for various pinch-off voltages VP for optimization of impurity flux density QDiff by diffusion process. The resulting I-V characteristics also show that the diffusion process introduces less process-induced damage compared to ion implantation, which suffers from current reduction due to a large number of defects introduced by the ion implantation process. Further the results show significant increase in gate-source capacitance Cgs and gate-drain capacitance Cgd for optical illuminations, where the photo-induced voltage has a significant role on gate capacitances. The switching time τ of the OPFET device is computed for dark and illumination conditions. The switching time τ is greatly reduced by optical illumination and is also a function of device active layer thickness and corresponding impurity flux density QDiff. Thus it is shown that the diffusion process shows great potential for improvement of optoelectronic devices in quantum efficiency and other performance areas.

Ferroic transitions in the multiferroic (1-x)Pb(Fe_1/2Nb_1/2)O₃-xPbTiO₃ system and its phase diagram

Singh, S.P.,Yusuf, S.M.,Yoon, S.,Baik, S.,Shin, N.,Pandey, D. Elsevier Science 2010 Acta materialia Vol.58 No.16

The results of the first comprehensive study of ferroic phase transitions as a function of temperature and compositions in the mixed multiferroic (1-x)Pb(Fe<SUB>1/2</SUB>Nb<SUB>1/2</SUB>)O<SUB>3</SUB>-xPbTiO<SUB>3</SUB> (PFN-xPT) system are reported. Temperature-dependent powder synchrotron X-ray diffraction studies confirm unambiguously an interferroelectric transition between monoclinic and tetragonal phases for x=<0.10. The tetragonal phase of PFN-xPT for x=<0.10 and x>0.10 is found to transform to the cubic phase on heating above room temperature. All these transitions are accompanied by distinct anomalies in the temperature dependence of dielectric constant. Our magnetization studies reveal that the nature of the magnetic phase transition changes across the morphotropic phase boundary (MPB) composition of PFN-xPT such that for tetragonal compositions with x>0.08 there is only one magnetic transition, whereas two antiferromagnetic transitions are observed for monoclinic compositions with x<0.08. These studies have enabled us to construct a phase diagram of PFN-xPT for the first time.

Simulation of 4H-SiC MESFET for High Power and High Frequency Response

Chattopadhyay, S.N.,Pandey, P.,Overton, C.B.,Krishnamoorthy, S.,Leong, S.K. The Institute of Electronics and Information Engin 2008 Journal of semiconductor technology and science Vol.8 No.3

In this paper, we report an analytical modeling and 2-D Synopsys Sentaurus TCAD simulation of ion implanted silicon carbide MESFETs. The model has been developed to obtain the threshold voltage, drain-source current, intrinsic parameters such as, gate capacitance, drain-source resistance and transconductance considering different fabrication parameters such as ion dose, ion energy, ion range and annealing effect parameters. The model is useful in determining the ion implantation fabrication parameters from the optimization of the active implanted channel thickness for different ion doses resulting in the desired pinch off voltage needed for high drain current and high breakdown voltage. The drain current of approximately 10 A obtained from the analytical model agrees well with that of the Synopsys Sentaurus TCAD simulation and the breakdown voltage approximately 85 V obtained from the TCAD simulation agrees well with published experimental results. The gate-to-source capacitance and gate-to-drain capacitance, drain-source resistance and trans-conductance were studied to understand the device frequency response. Cut off and maximum frequencies of approximately 10 GHz and 29 GHz respectively were obtained from Sentaurus TCAD and verified by the Smith's chart.

Optically Controlled Silicon MESFET Modeling Considering Diffusion Process

Chattopadhyay, S.N.,Motoyama, N.,Rudra, A.,Sharma, A.,Sriram, S.,Overton, C.B.,Pandey, P. The Institute of Electronics and Information Engin 2007 Journal of semiconductor technology and science Vol.7 No.3

An analytical model is proposed for an optically controlled Metal Semiconductor Field Effect Transistor (MESFET), known as Optical Field Effect Transistor (OPFET) considering the diffusion fabrication process. The electrical parameters such as threshold voltage, drain-source current, gate capacitances and switching response have been determined for the dark and various illuminated conditions. The Photovoltaic effect due to photogenerated carriers under illumination is shown to modulate the channel cross-section, which in turn significantly changes the threshold voltage, drainsource current, the gate capacitances and the device switching speed. The threshold voltage $V_T$ is reduced under optical illumination condition, which leads the device to change the device property from enhancement mode to depletion mode depending on photon impurity flux density. The resulting I-V characteristics show that the drain-source current IDS for different gate-source voltage $V_{gs}$ is significantly increased with optical illumination for photon flux densities of ${\Phi}=10^{15}\;and\;10^{17}/cm^2s$ compared to the dark condition. Further more, the drain-source current as a function of drain-source voltage $V_{DS}$ is evaluated to find the I-V characteristics for various pinch-off voltages $V_P$ for optimization of impurity flux density $Q_{Diff}$ by diffusion process. The resulting I-V characteristics also show that the diffusion process introduces less process-induced damage compared to ion implantation, which suffers from current reduction due to a large number of defects introduced by the ion implantation process. Further the results show significant increase in gate-source capacitance $C_{gs}$ and gate-drain capacitance $C_{gd}$ for optical illuminations, where the photo-induced voltage has a significant role on gate capacitances. The switching time ${\tau}$ of the OPFET device is computed for dark and illumination conditions. The switching time ${\tau}$ is greatly reduced by optical illumination and is also a function of device active layer thickness and corresponding impurity flux density $Q_{Diff}$. Thus it is shown that the diffusion process shows great potential for improvement of optoelectronic devices in quantum efficiency and other performance areas.

The dark nature of GRB 130528A and its host galaxy

Jeong, S.,Castro-Tirado, A. J.,Bremer, M.,Winters, J. M.,Gorosabel, J.,Guziy, S.,Pandey, S. B.,Jelí,nek, M.,Sá,nchez-Ramí,rez, R.,Sokolov, Ilya V.,Orekhova, N. V.,Moskvitin, A. S.,Te Springer-Verlag 2014 Astronomy and astrophysics Vol.569 No.-

Confirmation of the monoclinic Cc space group for the ground state phase of Pb(Zr_0.525Ti_0.475)O₃: A combined synchrotron X-ray and neutron powder diffraction study (5 pages)

Solanki, R.S.,Mishra, S.K.,Senyshyn, A.,Yoon, S.,Baik, S.,Shin, N.,Pandey, D. AMERICAN INSTITUTE OF PHYSICS 2013 APPLIED PHYSICS LETTERS Vol.102 No.5

Mating and Incidental Activities of Ram (Ovis aries) When Exposed to Ewe(s) and Competitor Ram in Pen Mating Condition

Patel, M.,Das, N.,Pandey, H.N.,Yadav, M.C.,Girish, P.S. Asian Australasian Association of Animal Productio 2005 Animal Bioscience Vol.18 No.4

An attempt was made to analyze the factors affecting mating performance of rams in pen mating systems. Due to many types of social interactions, mating performance of rams may decrease or increase. Six intact Muzaffarnagari rams were used and divided into three dominant subordinate pairs by food and ewe competition test. For dominant rams subordinate ram became competitor and vice versa. In the first experiment, ram was exposed to ewe but the competitor ram was kept outside the pen with the facility of visibility only. In the second experiment each ram was exposed to ewe along with the competitor ram and in third experiment ram was exposed to ewes (two) along with competitor ram in observation pen. Recordings of different mating and agonistic behaviour were done in all the experiments. It was found that subordinate ram's mating behaviour was inhibited by mere presence of a dominant ram out side without physical contact. However, when ram exposed to oestrus ewe(s) along with competitor ram, both dominant and subordinate rams spent much of their time in guarding activities instead of mating. In addition dominant ram tried to curtail the subordinate ram mating by agonistic interaction like fight and butting. Different guarding activities were observed either as active or passive type depending on level of dominanace. It was concluded that in a limited space the interaction of two or more rams might affect the number of services adversely.

Genetic Variability and Bottleneck Analysis of Jakhrana Goats by Microsatellite DNA Fingerprinting

Dinesh Kumar,A. K. Pandey,S. P. S. Ahlawat,Geetu Malik,Rekha Sharma,Digpal Singh Gour,S. P. Dixit,N. K. Verma,R. A. K. Aggarwal,Neelam Gupta,B. N. Shahi,S. C. Gupta 한국유전학회 2005 Genes & Genomics Vol.27 No.3

Structural, dielectric and photoluminescence properties of co-precipitated Zn-doped SnO2 nanoparticles

P.P. Sahay,R.K. Mishra,S.N. Pandey,S. Jha,M. Shamsuddin 한국물리학회 2013 Current Applied Physics Vol.13 No.3

Zn-doped SnO2 nanoparticles were prepared by the chemical co-precipitation route. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses of these prepared nanoparticles were carried out for structural and morphological studies. All the samples have been found to have tetragonal rutile structure of the polycrystalline SnO2 having crystallite size in the range 13e25 nm. TEM micrographs show agglomeration of nanoparticles in all the samples. At a particular temperature, the dielectric constant of all the samples has been found to decrease with increasing frequencies which may be due to rapid polarization processes occurring in SnO2 nanoparticles. The ac conductivity, s (u), has been found to vary with frequency according to the relation s (u) f uS. The value of S has been found to be temperature dependent, decreasing with increasing frequency which suggests that a hopping process is the most likely conduction mechanism in these nanoparticles. The room temperature photoluminescence (PL) spectra of the undoped and Zn-doped SnO2 nanoparticles consist of the near bandedge ultraviolet (UV) emission and the defect related visible emissions. The origin of emission peaks in the visible region is attributed to oxygen-related defects that are introduced during growth.