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Deep levels were observed using capacitance deep level optical spectroscopy (DLOS) in an AlGaN/GaN heterostructure equivalent to that of a heterojunction field effect transistor. Band gap states were assigned to either the AlGaN or GaN regions by comparing the DLOS spectra in accumulation and pinch-off modes, where the former reflects both AlGaN- and GaN-related defects, and the latter emphasizes defects residing in the GaN. A band gap state at E-c-3.85 eV was unambiguously identified with the AlGaN region, and deep levels at E-c-2.64 eV and E-c-3.30 eV were associated with the GaN layers. Both the AlGaN and GaN layers exhibited additional deep levels with large lattice relaxation. The influence of deep levels on the two-dimensional electron gas sheet charge was estimated using a lighted capacitance-voltage method. (c) 2006 American Institute of Physics.

Background: Heart is the principal organ of circulatory system that pumps blood into the blood vessels and performs many vital functions. Its development before birth must be studied to safeguard the animal from the occurrence and consequences of various developmental anomalies. The detailed morphometry of different external parameters of heart especially in pre-natal sheep has not yet been reported. Methods: The foeti of sheep were divided into three age groups viz. early prenatal (up to 50 days), mid prenatal (51-100 days) and late prenatal (101 to 150 days) with fifteen animals in each age group. The various external parameters were recorded by using digital weighing machine, graduated measuring cylinder, digital Vernier's calliper, non-stretchable nylon thread and graduated scale. The data recorded was statistically analysed by one way ANOVA with IBM SPSS 25.0 version software. Result: It was revealed that the average width of heart at its base was 4.82±0.22 mm, 10.52±0.72 mm and 21.57±1.03 mm in early prenatal, mid prenatal and late prenatal stages respectively. The average dorso-ventral length of left ventricle of heart was measured as 4.82±0.14 mm, 12.07±1.16 mm and 25.58±0.88 mm in early prenatal, mid prenatal and late prenatal stages respectively. The average distance between the left longitudinal groove and cranial border of heart at base was measured as 2.93±0.11 mm, 6.38±0.39 mm and 9.78±0.41 mm in early prenatal, mid prenatal and late prenatal stages respectively. Similarly, the average distance between the right longitudinal groove and cranial border of heart at middle was measured as 1.96±0.09 mm, 5.01±0.34 mm and 8.31±0.50 mm in early prenatal, mid prenatal and late prenatal stages respectively. All these parameters recorded showed significant (p ≤ 0.01) differences among the ages. [ABSTRACT FROM AUTHOR]

Prospective equivalent internal quantum efficiency (eta(int)) of approximately 34% at 300 K was demonstrated for the blue emission peak of nonpolar m-plane (1 (1) over bar 00) InxGa1-xN/GaN multiple quantum well light emitting diodes (LEDs) fabricated on freestanding m-plane GaN substrates. Although the eta(int) value is yet lower than that of conventional c-plane blue LEDs (> 70%), the results encourage one to realize high performance green, amber, and red LEDs by reducing the concentration of nonradiative defects, according to the absence of the quantum-confined Stark effects due to the polarization fields parallel to the quantum well normal. The electric field component of the blue surface emission was polarized perpendicular to the c axis with the in-plane polarization ratio of 0.58 at 300 K. (c) 2006 American Institute of Physics.

We report on the use of in-situ SiNx nanomask for defect reduction in nonpolar a-plane GaN films, grown by metal-organic chemical vapor deposition. High-resolution x-ray diffraction analysis revealed that there was a monotonic reduction in the full width at half maximum, both on-axis and off-axis, with the increase in the SiNx thickness. Atomic force microscopy images revealed a significant decrease in the root-mean-square roughness and the density of submicron pits. Cross-section and plan-view transmission electron microscopy on the samples showed that the stacking fault density decreased from 8x10(5) to 3x10(5) cm(-1) and threading dislocation density decreased from 8x10(10) to 9x10(9) cm(-2). Room temperature photoluminescence measurement revealed that the band-edge emission intensity increased with the insertion of the SiNx layer, which suggests reduction in the nonradiative recombination centers. (c) 2006 American Institute of Physics.

The impact of threading dislocation density on Ni/n-GaN Schottky barrier diode characteristics is investigated using forward biased current-voltage-temperature (I-V-T) and internal photoemission (IPE) measurements. Nominally, identical metal-organic chemical vapor deposition grown GaN layers were grown on two types of GaN templates on sapphire substrates to controllably vary threading dislocation density (TDD) from 3x10(7) to 7x10(8) cm(-2). I-V-T measurements revealed thermionic emission to be the dominant transport mechanism with ideality factors near 1.01 at room temperature for both sample types. The Schottky barrier heights showed a similar invariance with TDD, with measured values of 1.12-1.13 eV obtained from fitting the I-V-T results to a thermionic emission-diffusion model. The I-V-T results were verified by IPE measurements made on the same diodes, confirming that the Ni/n-GaN barrier heights do not show a measurable TDD dependence for the TDD range measured here. In apparent contrast to this result is that the measured forward bias I-V characteristics indicate a shift in the observed forward bias turn-on voltage such that at the higher TDD value investigated here, a larger turn-on voltage (lower current) is observed. This difference is attributed to localized current blocking by high potential barrier regions surrounding threading dislocations that intersect the Ni/GaN interface. A simple model is presented that reconciles both the observed voltage shift and variations in the extracted Richardson constant as a function of threading dislocation density. With this model, an average local barrier surrounding dislocation of similar to 0.2 V is obtained, which diverts current flow across the forward biased Schottky interface to nondislocated regions. (c) 2006 American Institute of Physics.

This letter reports AlGaN/GaN high-electron mobility transistors with capless activation annealing of implanted Si for nonalloyed ohmic contacts. Source and drain areas were implanted with an Si dose of I x 10(16) cm(-2) and were activated at similar to 1260 degrees C in a metal-organic chemical vapor deposition system in ammonia and nitrogen at atmospheric pressure. Nonalloyed ohmic contacts to ion-implanted devices showed a contact resistance of 0.96 Omega (.) mm to the channel. An output power density of 5 W/mm was measured at 4 GHz, with 58% power-added efficiency and a gain of 11.7 dB at a drain bias of 30 V.

In this letter, unpassivated high power deeply recessed GaN-based high electron mobility transistors (HEMTs) are reported. The introduction of a thick graded AlGaN cap layer and a novel fluorine-plasma surface treatment reduced the gate-leakage current and increased breakdown voltage significantly, enabling the application of much higher drain biases. Due to excellent dispersion suppression achieved at an epitaxial level, an output power density of more than 17 W/mm with an associated power added efficiency (PAE) of 50% was measured at 4 GHz and V-DS = 80 V without SiNx passivation. These results demonstrate the great potential of this novel epitaxial approach for passivation-free GaN-based HEMTs for high-power applications.

We investigated the suitability of ZrO2 as a high-k dielectric for GaN material systems. Thin Zr films (4 nm) were deposited by electron-beam evaporation at room temperature oil n-type GaN and Al(0.22)Gao(0.78)N (29 nm)/GaN high electron mobility transistor (HEMT) structures. The Zr-coated samples were subsequently oxidized at temperatures in the range of 200-400 degrees C in an ozone environment. Atomic force microscopy studies after oxidation show that the ZrO2 forms a conformal layer on the underlying GaN template. Cross-section transmission electron microscopy studies showed little intermixing of the ZrO2 with the AlGaN/GaN. The relative dielectric constant of the ZrO2 was determined to be 23. In comparison with HEMTs with bare gates (no dielectric between the gate metal and AlGaN), the HEMTs with ZrO2 showed two to three order of magnitude reduction in gate leakage current. Optimization of the HEMT process on sapphire substrates with ZrO2 under the gates yielded devices with powers of 3.8 W/mm and 58% power-added efficiency at 4 GHz. (c) 2006 American Vacuum Society.

Recombination dynamics of the 268 nm photoluminescence (PL) peak in a quaternary Al0.53In0.11Ga0.36N/Al0.58In0.02Ga0.40N multiple quantum well (MQW) grown on relaxed AlGaN templates were studied. Although the polarization field in the compressively strained Al0.53In0.11Ga0.36N wells was as high as 1.6 MV/cm, the value of integrated PL intensity at 300 K divided by that at 8 K (eta(int)) was as high as 1.2%. The value was similar to that obtained for the 285 nm PL peak in an Al0.30Ga0.70N/Al0.70Ga0.30N MQW (1.3%), though the A1N molar fraction in the wells was higher by a factor of 1.7. According to these results and the fact that time-resolved PL signal exhibited a stretched exponential decay shape, the improved eta(int) of the AlInGaN wells was attributed to a beneficial effect of the exciton localization as is the case with InGaN alloys; doping or alloying with InN was confirmed to work also on AlGaN in improving eta(int) to realize deep UV optoelectronic devices.

The electrical conductivity and deep level spectrum of GaN grown by molecular beam epitaxy and codoped with carbon and silicon were investigated for substrate temperatures T-s of 650 and 720 degrees C as a function relative carbon and silicon doping levels. With sufficiently high carbon doping, semi-insulating behavior was observed for films grown at both temperatures, and growth at T-s=720 degrees C enhanced the carbon compensation ratio. Similar carbon-related band gap states were observed via deep level optical spectroscopy for films grown at both substrate temperatures. Due to the semi-insulating nature of the films, a lighted capacitance-voltage technique was required to determine individual deep level concentrations. Carbon-related band gap states underwent substantial redistribution between deep level and shallow acceptor configurations with change in T-s. In light of a T-s dependence for the preferential site of carbon incorporation, a model of semi-insulating behavior in terms of carbon impurity state incorporation mediated by substrate temperature is proposed. (c) 2006 American Institute of Physics.

Polarization gradients in graded AlGaN alloys induce bulk electron distributions without the use of impurity doping. Since the alloy composition is not constant in these structures, the electron scattering rates vary across the structure. Capacitance and conductivity measurements on field effect transistors were used to find mobility as a function of depth. The effective electron mobility at different depths calculated from theory closely matched the measured mobility. Local bulk mobility values for different AlGaN compositions were found, and the electron mobility in AlGaN as a function of alloy composition was deduced. These were found to match with theoretical calculations. (c) 2006 American Institute of Physics.

We report on the fabrication and high-frequency characterization of AlGaN/GaN high-electron mobility transistors (HEMTs) grown by molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). In devices with a gate length of 160 nm, a record power density of 10.5 W/mm with 34% power added efficiency (PAE) has been measured at 40 GHz in MOCVD-grown HEMTs biased at V-DS = 30 V. Under similar bias conditions, more than 8.6 W/mm, with 32% PAE, were obtained on the MBE-grown sample. The dependence of output power, gain, and PAE on gate and drain voltages, and frequency have also been analyzed.

Titanium dioxide (TiO2, with the rutile structure) was grown on (0001) oriented GaN and (0001) Al0.33Ga0.67N/GaN heterostructure field effect transistor (HFET) structures by molecular beam epitaxy. X-ray diffraction showed (100)TiO2 parallel to (0001)(GaN(AlGaN)) and [001](TiO2) parallel to (GaN(AlGaN)) with three rotational variants of the TiO2. Transmission electron microscopy of 50 nm thick TiO2 films on GaN and AlGaN/GaN showed sharp interfaces with no intermixing or reaction between the oxide and semiconductor. The TiO2 exhibited a columnar film microstructure with a lateral domain size of a few nanometers parallel to (10 (1) over bar)(TiO2) and a few tens of nanometers parallel to 00160 2 2 Metal-oxide HFIAs with 50 nm thick TiO2 dielectric layers under the gate were processed and compared to HFETs without the TiO2 dielectric layer. The transconductance of the HFETs with TiO2 was 140 MS/mm, approximately 20% less than HFETs with no dielecric, and the pinchoff voltages of the two stuctures were comparable. The dielectric constant of the TiO2 was similar to 70. The gate leakage current of the HFETs with ,TiO2, similar to 4 X 10(-6) mA/mm at. 50 V, was approximately 4 orders of magnitude lower than that of the. HFETs with no dielectric. Band offset measurements were performed using x-ray photoelectron spectroscopy, and the valence band of the rutile TiO2 and the GaN nearly line up. (c) 2005 American Vacuum Society.

AlGaN/GaN current aperture vertical electron transistor (CAVET) was fabricated and optimized for band gap selective photoelectrochemical wet etching. The large polarization induced voltage offset (around 2.5-4 eV) observed in the first generation CAVET was reduced to 0.7 V in this structure by employing a delta Si doping layer buried 60 Angstrom below the In0.03Ga0.97N (60 nm thick) and bottom GaN interface to screen the polarization fields. Other sample structures were studied to achieve an aperture with both good undercut etching and a small voltage offset. It was clearly demonstrated that etch selectivity in the GaN/InGaN/GaN undercut structures was influenced by hole confinement and the chemical activity of the N-face GaN. (C) 2004 American Institute of Physics.

Carbon tetrabromide (CBr4) was studied as an intentional dopant during rf plasma molecular beam epitaxy of GaN. Secondary ion mass spectroscopy was used to quantify incorporation behavior. Carbon was found to readily incorporate under Ga-rich and N-rich growth conditions with no detectable bromine incorporation. The carbon incorporation [C] was found to be linearly related to the incident CBr4 flux. Reflection high-energy electron diffraction, atomic force microscopy and x-ray diffraction were used to characterize the structural quality of the film's postgrowth. No deterioration of structural quality was observed for [C] from mid 10(17) to similar to10(19) cm(-3). The growth rate was also unaffected by carbon doping with CBr4. The electrical and optical behavior of carbon doping was studied by co-doping carbon with silicon. Carbon was found to compensate the silicon although an exact compensation factor was difficult to extract from the data. Photoluminescence was performed to examine the optical performance of the films. Carbon doping was seen to monotonically decrease the band edge emission. Properties of carbon-doped GaN are interpreted to be consistent with recent theoretical work describing incorporation of carbon as function of Fermi level conditions during growth. (C) 2004 American Institute of Physics.

We report AlGaN-GaN high electron mobility transistors (HEMTs) grown by molecular beam epitaxy (MBE) on SiC substrates with excellent microwave power and efficiency performance. The GaN buffers in these samples were doped with carbon to make them insulating. To reduce gate leakage, a thin silicon nitride film was deposited on the AlGaN surface by chemical vapor deposition. At 4 GHz, an output power density of 6.6 W/mm was obtained with 57% power-added efficiency (PAE) and a gain of 10, dB at a drain bias of 35 V. This is the highest PAE reported until now at 4 GHz in AlGaN-GaN HEMTs grown by MBE. At 10 GHz, we measured an output power density of 7.3 W/mm with a PAE of 36% and gain of 7.6 dB at 40-V drain bias.

High-voltage Al0.22Ga0.78N-GaN high-electron mobility transistors have been fabricated using multiple field plates over dielectric passivation layers. The device breakdown voltage was found to increase with the addition of the field plates. with two field plates, the device showed, a breakdown voltage as high as 900 V. This technique is easy to apply, based on the standard planar transistor fabrication, and especially attractive for the power switching applications.

We discuss an AlGaN/GaN metal-semiconductor field-effect transistor (MESFET) structure grown without any impurity doping in the channel. A high-mobility polarization-induced bulk channel charge was created by grading the channel region linearly from GaN to Al0.3Ga0.7N over 1000 Angstrom. This polarization-doped FET (PolFET) was fabricated and tested under dc and rf conditions. Current density of 850 mA/mm and transconductance of 93 mS/mm was observed under dc conditions. The 0.7 mum gate length devices had a cutoff frequency, f(tau)=19 GHz, and maximum oscillation frequency, f(max)=46 GHz. We demonstrate that the PolFETs perform better than comparable MESFETs with impurity-doped channels, and are suitable for high power microwave applications. An important advantage of these devices over AlGaN/GaN high electron mobility transistors is that the transconductance versus gate voltage profile can be tailored by compositional grading for better large-signal linearity. (C) 2004 American Institute of Physics.

AlGaN/GaN current aperture vertical electron transistors with regrown aperture and source regions have been fabricated and tested. A 2 mum thick GaN:Si drain region followed by a 0.4 mum GaN:Mg current-blocking layer were grown by metalorganic chemical vapor deposition on a c-plane sapphire substrate. Channel apertures were etched, and a maskless regrowth was performed to grow unintentionally doped GaN inside the aperture as well as above the insulating layer, and to add an AlGaN cap layer. Cl-2 reactive ion etching was used to pattern the device mesa, and source, drain, and gate metals were then deposited. Devices were achieved with a maximum source-drain current of 750 mA/mm, an extrinsic transconductance of 120 mS/mm, and a 2-terminal gate breakdown of 65 V while exhibiting almost no DC-RF dispersion for 80 mus pulsed I-V curves. The suppression of DC-RF dispersion was shown to result from the absence of the large electric fields at the surface on the drain-side edge of the gate that are present in high electron mobility transistors. Parasitic leakage currents, which were present in all devices, have been studied in detail. Three leakage paths have been identified, and methods to eliminate them are discussed. (C) 2004 American Institute of Physics.

This letter describes the relationship between the morphological evolution of heteroepitaxial a-plane GaN films and the formation of the extended defect structure. The initial a-plane GaN growth on a-plane SiC substrates (via a high temperature AlN buffer layer) follows a Volmer-Weber growth mode. Consequently, the coalescence of three-dimensional (3D) islands generates threading dislocations which dominate the nonpolar GaN film's microstructure (3x10(10) cm(-2)). Exposed nitrogen-face surfaces, identified using x-ray diffraction measurements and convergent beam electron diffraction analysis, are present throughout the 3D growth and are the likely source of basal plane faulting (7x10(5) cm(-1)) within the film. Atomic force microscopy and scanning electron microscopy were used to image the morphological transition, which was correlated to changes in the a-GaN crystal tilt mosaic measured by x-ray rocking curves. (C) 2004 American Institute of Physics.

Cathodoluminescence technique combined with transmission electron microscopy (TEM-CL) has been used to characterize optical properties of dislocations in GaN epilayers. The dislocations act as nonradiative centers with different recombination rates. TEM-CL observation showed that even for the same Burgers vector of a, the dislocations show different electrical activity depending on the direction of dislocation line, i.e., the edge-type dislocation parallel to the c plane is very active, while the screw-type one is less active. The simulation of the CL images gives us the information of parameters such as carrier lifetime and diffusion length. (C) 2003 American Institute of Physics.

Evaluation of the structural properties of 200-nm-thick Si-doped Al0.49Ga0.51N films, grown on nominally relaxed 1-mum-thick Al0.62Ga0.38N buffer layers on sapphire, revealed that increased Si doping promoted the relaxation of the compressively strained layers. The degree of strain relaxation R of the Al0.49Ga0.51N films, as determined by x-ray diffraction (XRD), increased from R=0.55 to R=0.94 with an increase in disilane injection from 1.25 nmol/min to 8.57 nmol/min. Transmission electron microscopy analysis showed that the edge threading dislocations (TDs) in the Al0.49Ga0.51N layers were inclined, such that the redirected TD lines had a misfit dislocation component. The calculated strain relaxation due to the inclined TDs was in close agreement with the values determined from XRD. We propose that the TD line redirection was promoted by the Si-induced surface roughness. (C) 2003 American Institute of Physics.

Mg doping has been found in some situations to invert growth on Ga-face GaN to N-face. In this study, we clarified the role the Ga wetting layer plays in rf plasma molecular beam epitaxy of GaN when Mg doping, for [Mg] from similar to2 X 10(19) to similar to1 X 10(20) cm(-3) corresponding to the useful, accessible range of hole concentrations of p similar to 10(17)-10(18) cm(-3) Structures were grown in the N-rich and Ga-rich growth regime for single Mg doping layers and for multilayer structures with a range of Mg concentrations. Samples were characterized in situ by reflection high-energy electron diffraction and ex situ by atomic force microscopy, transmission electron microscopy, convergent beam electron diffraction, and secondary ion mass spectroscopy. Growth on "dry" surfaces (without a Ga wetting layer) in the N-rich regime completely inverted to N-face upon exposure to Mg. No reinversion to Ga-face was detected for subsequent layers. Additionally, Mg was seen to serve as a surfactant during this N-rich growth, as has been reported by others. Growth initiated in the Ga-rich regime contained inversion domains that nucleated with the initiation of Mg doping. No new inversion domains were found as the Mg concentration was increased through the useful doping levels. Thus the Ga wetting layer was found to inhibit nucleation of N-face GaN, though a complete wetting layer took time to develop. Finally, by establishing a complete Ga wetting layer on the surface prior to growth, we confirmed this finding and demonstrated Mg-doped GaN completely free from inversion domains to a doping level of [Mg] similar to2 X 10(20). (C) 2003 American Vacuum Society.

The influence of AlGaN and GaN cap layer thickness on Hall sheet carrier density and mobility was investigated for Al0.32Ga0.68N/GaN and GaN/Al0.32Ga0.68N/GaN heterostructures deposited on sapphire substrates. The sheet carrier density was found to increase and saturate with the AlGaN layer thickness, while for the GaN-capped structures it decreased and saturated with the GaN cap layer thickness. A relatively close fit was achieved between the measured data and two-dimensional electron gas densities predicted from simulations of the band diagrams. The simulations also indicated the presence of a two-dimensional hole gas at the upper interface of GaN/AlGaN/GaN structures with sufficiently thick GaN cap layers. A surface Fermi-level pinning position of 1.7 eV for AlGaN and 0.9-1.0 eV for GaN, and an interface polarization charge density of 1.6x10(13)-1.7x10(13) cm(-2), were extracted from the simulations. (C) 2003 American Institute of Physics.

Shubnikov-de-Haas oscillation is observed in a polarization-doped three-dimensional electron slab in a graded AlxGa1-xN semiconductor layer. The electron slab is generated by the technique of grading the polar semiconductor alloy with spatially changing polarization. Temperature-dependent oscillations allow us to extract an effective mass of m*=0.21m(0). The quantum scattering time measured (tau(q)=0.3 ps) is close to the transport scattering time (tau(t)=0.34 ps), indicating the dominance of short-range scattering. Alloy scattering is determined to be the dominant mechanism-limiting mobility; this enables us to extract an alloy-scattering parameter of V-0=1.8 eV for the AlxGa1-xN material system. Polarization-doping presents an exciting technique for creating electron slabs with widely tunable density and confinement for the study of dimensionality effects on charge transport and collective phenomena.

N-p-n Al0.05GaN/GaN heterojunction bipolar transistors with a common emitter operation voltage higher than 330 V have been demonstrated using selectively regrown emitters. Devices were grown by metalorganic chemical vapor deposition on sapphire substrates. The n-type emitter was grown selectively on a 100-nm-thick p-base with an 8 mum n-collector structure using a dielectric mask. The shallow etch down to the collector mitigates damages induced in the dry etch, resulting a low leakage and a high breakdown. The graded AlGaN emitter results in a common emitter current gain of similar to18 at an average collector current density of up to 1 kA/cm(2) at room temperature.

Background: Heart is the central organ of circulatory system that pumps blood into the blood vessels and performs many vital functions. Its development before birth must be studied to safeguard the animal from the occurrence and consequences of various developmental anomalies. The detailed morphometry of different internal parameters of heart especially in pre-natal sheep has not yet been reported. Methods: The foeti of sheep were divided into two age groups viz. mid prenatal (51-100 days) and late prenatal (101 to 150 days) with fifteen animals in each age group. The various internal parameters were recorded by using digital weighing machine, graduated measuring cylinder, digital Vernier’s calliper, non-stretchable nylon thread and graduated scale. The data recorded was statistically analysed by independent t test with IBM SPSS 25.0 version software. Result: The average thickness of left ventricular wall of heart was measured as 2.85±0.15 mm and 4.28±0.07 mm in mid prenatal and late prenatal stages respectively with significant (p≤0.01) differences between the ages. Similarly, the average diameter of left atrio-ventricular opening of heart was measured as 2.06±0.27 mm and 6.08±0.36 mm in mid prenatal and late prenatal stages respectively with significant (p≤0.01) differences between the ages. The average length of septal papillary muscle in right ventricle was measured as 1.12±0.10 mm and 3.29±0.21 mm in mid prenatal and late prenatal stages respectively with significant (p≤0.01) differences between the ages. Further, the average length of moderator band in heart was measured as 1.45±0.11 mm and 4.34±0.23 mm in mid prenatal and late prenatal stages respectively with significant (p≤0.01) differences between the ages. Similarly, the average length of chordae tendinae in right ventricle of heart was measured as 0.97±0.09 mm and 3.50±0.34 mm in mid prenatal and late prenatal stages respectively with significant (p≤0.01) differences between the ages. [ABSTRACT FROM AUTHOR]

Background: It is known that balance diet is the key success for better production in poultry. The digestive physiology is regulated by the neurocrine and endocrine secretions. Growth, secretion, motility, cell signalling, vasoregulation, cell proliferation and differentiation of the epithelial cells of the alimentary canal are reported to be controlled by the peptides or amines released from the gut endocrine cells and enteric neurons. References particularly on systematic study of gastrointestinal endocrine cells in duck as regards to histomorphology and cytochemistry are gravely scanty. Hence the present investigation envisages authenticating the histomorphological characters and cytochemical behaviour of the gastrointestinal endocrine cells in duck. Methods: For this study the abdomen of six Khaki campbell ducks from either sex was cut open following euthanasia. Tissue pieces from different segments of gut were collected and processed routinely to get 7-8 µ thick serial paraffin sections. The tissue sections were stained for evaluation of histomorphological and histochemical characters of the entero-endocrine cells. Result: A panel of seven cytochemical stains identified nine endocrine cell types in the digestive mucosa of Khaki Campbell duck i.e. basally granulated oval cell, densely granulated spindle shaped cell, densely granulated oval cell, diffusely granulated oval cell, pyramidal cell, densely granulated elongated cell, densely granulated pyriform cell, peripherally granulated spherical cell and nonargentaffin chromaffin oval cell. The cells occurred in single or in small clusters in the basal or middle or neck part of glandular epithelium or in the surface epithelium. All the endocrine cells were 'close type'. Cytochemically they were four types i.e. argentaffin, argyrophil, chromaffin and APUD (Amine precursor uptake and decarboxylation) cells. [ABSTRACT FROM AUTHOR]

Background: Hansli chicken is reared in Mayurbhanj and Keonjhar districts of Odisha. They play a vital role in the economic upliftment of poor, landless and marginalised people in the rural areas besides providing them with nutritious egg and meat for consumption. Methods: Hansli chicks and Vencobb broiler chicks were divided into three age groups viz. group I (up to 1 month), group II (1-3 months) and group III (3-6 months) with six birds in each age group. On 4th week, 12th week and 24th week, six birds from each breed were used for the study of histomorphometrical features of the thymus, spleen and bursa of Fabricius. Result: The average thickness of the capsule, cortex and medulla of thymus, average width of thymic lobule and average maximum diameter of Hassall’s corpuscles differed significantly (p0.05) between the birds at specific ages. Similarly, the average thickness of the splenic capsule, average width of white pulp, average external transverse and internal longitudinal diameters of trabecular artery, average external longitudinal, internal longitudinal, external transverse and internal transverse diameters of central artery, average longitudinal diameter of capillary, average longitudinal and transverse diameters of splenic nodule, average thickness of PALS and PELS differed significantly (p0.05) between the birds at specific ages. The average number of bursal follicles in larger and smaller plicae, average height and width of larger and smaller plicae, average length and width of bursal follicle, average height of columnar cell of pseudostratified FAE and IFE, average nuclear height of FAE and IFE columnar cells differed significantly (p0.05) between the birds at specific ages. [ABSTRACT FROM AUTHOR]

P-n diodes and metal-oxide-semiconductor-capacitors (MOSCAPs) are integral parts of vertical GaN power MOSFETs. The voltage in the off-state in trench MOSFETs is held by the p-n junction (source-drain) and the MOSCAP (gate-drain). Although the understanding of the reverse bias behavior of the p-n diode and the MOSCAP component is critical, the literature is sparse pertaining to the reverse bias studies of GaN MOSCAPs. In this work, we present a detailed investigation on the reverse bias behavior of in situ grown GaN MOSCAPs. A photo-assisted I-V technique is also presented to estimate the reverse breakdown field of the gate-dielectric. [ABSTRACT FROM AUTHOR]

A new model of computation called Watson–Crick jumping finite automata was introduced by Mahalingam et al. , and the authors study the computing power and closure properties of the variants of the model. There are four variants of the model: no state, 1-limited, all-final and simple Watson–Crick jumping finite automata. In this paper, we introduce a restricted version that is a combination of variants of the existing model. It becomes essential to explore the computing power and closure properties of these combinations. The combination variants are extensively compared with Chomsky hierarchy, general jumping finite automata family and among themselves. We also explore the closure properties of such restricted automata. [ABSTRACT FROM AUTHOR]