Anomalous Hall effect was observed at room temperature in MOCVD-grown GaGdN from a (TMHD)3Gd source, which can contain oxygen in its organic ligand. GaN, and GaGdN grown using a Cp3Gd precursor which does not contain oxygen only showed the ordinary Hall effect. This indicates that oxygen could have a role in magnetic properties of GaGdN. The relationship between the anomalous Hall conductivity and longitudinal conductivity indicated that metallic conduction, hopping of carriers, and scattering-independent mechanisms are likely responsible for the ferromagnetism. However, this still requires further clarification.

In this work, temperature-dependent optical properties of a series of AlN thin films with different thickness are studied by spectroscopic ellipsometry (SE) ranging from 300 to 825K. The fitted refractive index at 300K is in good agreement with the reported by others, which confirms the high accuracy of the optical model used in this work. The degradation of the absorption properties and the decrease of the bandgap become more pronounced with temperature increases above 475K. A larger change of bandgap at elevated temperature is observed for the thinner AlN epi-layer (300nm) than the thicker ones (404nm). This can be attributed to the poor surface morphologies and crystal qualities in the thinner AlN epi-layer.

Animal-source foods (ASF) have the potential to enhance the nutritional adequacy of cereal-based diets in low- and middle-income countries, through the provision of high-quality protein and bioavailable micronutrients. The development of guidelines for including ASF in local diets requires an understanding of the nutrient content of available resources. This article reviews food composition tables (FCT) used in sub-Saharan Africa, examining the spectrum of ASF reported and exploring data sources for each reference. Compositional data are shown to be derived from a small number of existing data sets from analyses conducted largely in high-income nations, often many decades previously. There are limitations in using such values, which represent the products of intensively raised animals of commercial breeds, as a reference in resource-poor settings where indigenous breed livestock are commonly reared in low-input production systems, on mineral-deficient soils and not receiving nutritionally balanced feed. The FCT examined also revealed a lack of data on the full spectrum of ASF, including offal and wild foods, which correspond to local food preferences and represent valuable dietary resources in food-deficient settings. Using poultry products as an example, comparisons are made between compositional data from three high-income nations, and potential implications of differences in the published values for micronutrients of public health significance, including Fe, folate and vitamin A, are discussed. It is important that those working on nutritional interventions and on developing dietary recommendations for resource-poor settings understand the limitations of current food composition data and that opportunities to improve existing resources are more actively explored and supported.

Thermoelectric (TE) materials have gained renewed interests in last decades for both power generation and energy conservation from waste-heat harvesting. Research in the discovery of best TE materials such as, bulk materials, complex structures, and low dimensional play crucial role to achieve high efficiency TE materials. Wide bandgap materials like ZnO can be promising candidate for high efficiency TE power generation owing to its low-cost, nontoxicity, and stability at high temperatures. In this paper, room temperature TE properties of thin film ZnO grown by metal organic vapor deposition (MOCVD) are reported. TE properties of thin film GaN are also studied as reference to that of thin film ZnO. Moreover, high resolution x-ray diffraction (HRXRD), room temperature photoluminescence (PL) with deep ultraviolet (DUV) spectroscopy (excitation at 248nm), hall effect, and thermal gradient methods have been employed to investigate the effect of structural, optical, electrical, and thermal properties of the samples, respectively. The effect of doping concentrations and structural defects on Seebeck coefficients of thin film ZnO are systematically studied and discussed in this work.

GaN and its alloys are promising candidates for high temperature thermoelectric (TE) materials due to their high Seebeck coefficient and high thermal and mechanical stability. Moreover, these materials can overcome the toxicity concern of current Te-based TE materials, such as Bi2Te3 and PbTe. These materials have recently shown a higher Seebeck coefficient than that of SiGe in high temperature region because their large bandgap characteristic eliminates the bipolar conduction. In this study, we report the room temperature thermoelectric properties of p-type Mg doped GaN, grown by metalorganic chemical vapor deposition (MOCVD) on sapphire substrate with various carrier concentrations. Undoped and n-type GaN are also incorporated with p-type GaN films to make comparison. The structural, optical, electrical, and thermal properties of the samples were examined by X-ray diffraction, photoluminescence, van der Pauw hall-effect, and thermal gradient methods, respectively. The Seebeck coefficient ranging from 710-900µV/K at room temperature of Mg: GaN were observed, which further indicated their potential TE applications.

In this study, thermoelectric properties of bulk and epitaxy GaN with various doping concentration are investigated. Seebeck coefficients decreased with the increase of carrier concentration for both bulk and epitaxial GaN samples, and the Seebeck coefficients of epitaxial GaN samples are found to be larger than that of bulk GaN samples in the similar carrier density due to the higher dislocation scattering. For epitaxial samples, a high power factor of 4.72 × 10-4 W/m-K2 is observed. The power factors of the bulk GaN samples are in the range of from 0.315× 10-4W/m-K2 to 0.354× 10-4W/m-K2 due to the low Seebeck coefficients.

The mechanism leading to RT ferromagnetism in Gd-doped GaN is not agreed upon, despite many experimental and theoretical reports. Oxygen impurities have been proposed as a possible contributor to ferromagnetic behavior in GaN:Gd films. In this report, GaN:Gd thin films grown by MOCVD using two different metalorganic Gd precursors are examined. The two precursors are (TMHD)3Gd, which contains oxygen, and Cp3Gd, which does not. The films have been characterized by XRD, VSM, and EDS. EDS measurements indicate that the TMHD3Gd samples contain oxygen, while the Cp3Gd samples do not, and VSM scans show that the TMHD3Gd samples exhibit much higher magnetic moments than the Cp3Gd samples, supporting the theory that oxygen enhances the ferromagnetic behavior of GaN:Gd.

The emission from a light emitting diode (LED) that is emitted under the metal electrode cannot escape into free space. A current blocking layer (CBL) is used to address this issue by forcing the current to flow laterally under the electrode reducing the emission absorbed and hence increasing the overall efficiency of the LED. In this paper a new method to fabricate Schottky and isolating CBLs in GaN LED are investigated. Optical and electrical measurements of these vertical LEDs with and without CBL show different light output powers at identical current densities. The results of this study indicate that CBLs could also be used to suppress the efficiency droop effect for GaN LEDs.

In this paper the thermoelectric properties–the Seebeck coefficient, the electrical conductivity and the power factor – of GaN and InGaN thin films grown by Metal Organic Vapor Deposition (MOCVD) are reported. The Seebeck coefficient and power factor of InGaN decreases with increasing indium content, although the electrical conductivity shows an inverse behavior. P-type doped samples demonstrated the highest Seebeck coefficient (637 μV/K in GaN:Mg, 1200 μV/K in InGaN:Mg) but the lowest power factor (0.1x10-4 W/m-K for GaN:Mg, 0.4x10-4 W/m-K for InGaN:Mg). The Seebeck coefficient of the doped GaN thin films decreased linearly with log of the carrier concentration. GaN:Si exhibited a maximum power factor of 9.1x10-4 W/m-K with a carrier concentration of 1.6x1018 cm-3, and In0.1Ga0.9N exhibited a maximum power factor of 109x10-4 W/m-K with a carrier concentration of 1.2x1018 cm-3. The results also indicate that GaN and InGaN-based materials could potentially be useful materials for TE applications at high temperatures.

Thin film gallium nitride (GaN) scintillators have been produced by MOCVD and made neutron-sensitive by applying an enriched lithium-6 fluoride (6LiF) conversion layer. The 6Li(n,α) reaction produces both alpha and triton particles, which have very penetration depths in GaN. The range and energy deposition characteristics of these particles in GaN have been simulated. Alpha-induced scintillation was measured in silicon-doped GaN using an americium-241 (241Am) source. The thermal neutron responses of the 6LiF-coated GaN scintillator were tested using two thermal neutron sources, an 241Am-Be source inside a graphite pile and a reactor source. The scintillator was found to have a linear response to thermal neutron flux level over a range of more than three orders of magnitude.

In this work, a room temperature spin-polarized LED based on ferromagnetic Ga1-xGdxN is reported. The device was grown by metalorganic chemical vapor deposition (MOCVD) and is the first report of a spin-LED based on Ga1-xGdxN. Electroluminescence from this device had a degree of polarization of 14.6% at 5000 Gauss and retained a degree of polarization of 9.3% after removal of the applied magnetic field. Ga1-xGdxN thin films were grown on 2 μm GaN templates and were co-doped with Si and Mg to achieve n-type and p-type materials. Co-doping of the Ga1-xGdxN films with Si produced conductive n-type material, while co-doping with Mg produced compensated p-type material. Both Si and Mg co-doped films exhibited room temperature ferromagnetism, measured by vibrating sample magnetometry.

GaN-based dilute magnetic semiconductors (DMS) have recently been investigated for use in spintronic devices. In particular, Gd-doped GaN has shown very promising room temperature ferromagnetic behavior and potential for use in spintronics applications. III-Nitride materials have recently had their thermoelectric properties investigated; however this work has not been extended to Nitride-based DMS. Understanding the spin-calorimetric characteristics of GaN-based DMS is important to the successful development of low-power spintronic devices. In this paper the Seebeck and spin-Seebeck effect in MOCVD grown Gd-doped GaN (Gd: GaN) are investigated.

Strong polarization effects observed in III-nitride materials can invert the surface carrier type. The corresponding band bending can be used to design InGaN solar cells. Similar surface inversion was observed in the past with silicon-based Schottky-barrier solar cells, but was limited by Fermi level pinning. The formation of two-dimensional electron gas by polarization fields in III-nitrides has been reported. Using a similar idea, the growth of a thin AlN capping layer on p-InGaN has resulted in band bending, hence depletion region, under the surface that can be used separate any generated photo-carriers. Hall measurements at different depths on these structures confirm the inversion of surface carrier type. Solar cells based on this concept have resulted in an open circuit voltage of 2.15 V and short circuit current of 21.8 μA.

Crystalline perfection of InGaN epi-layers is the missing design parameter for InGaN solar cells. Structural deterioration of InGaN epi-layers depends on the thickness, composition and growth conditions as well. Increasing the InGaN epi-layer thickness beyond a critical point introduces extended crystalline defects that hinder the optical absorption and electrical properties. Increasing the InGaN composition further reduces this critical layer thickness. The optical absorption band edge is sharp for III-nitride direct band gap materials. The band edge profile is deteriorated by creation of extended crystalline defects in the InGaN epitaxial material. The design of InGaN solar cells requires the growth of epi-layers where a trade off between crystalline perfection and optical absorption properties is reached.