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Compost bedded pack (CBP) barns have been receiving increased attention as an alternative housing system for dairy cattle. To create a satisfactory environment within CBP barns that promotes a good composting process, an adequate air movement and minimal temperature fluctuations throughout the building are required. Therefore, a study based on compost barn structure model employing techniques of dimensional analysis for naturally ventilated buildings was developed. Three-dimensional computational fluid dynamic (CFD) simulations of compost barns with different ridge designs and wind direction, along with the visual demonstration of the impact on airflow through structure were performed. The results showed that the barn ventilation CFD model and simulations were in good agreement with the experimental measurements, predicting the airflow through the CBP barns structure for alternative roof ridge types adequately. The results also indicate that the best roof configuration in the winter was the open ridge with chimney for a west to east wind direction.

C26H30N2, monoclinic, C12/c1 (no. 15), a = 20.434(2) Å, b = 8.551(1) Å, c = 26.498(2) Å, β = 102.889(1)°, V = 4513.4 Å3, Z = 8, Rgt(F) = 0.062, wRref(F2) = 0.187, T = 293 K.

C29H36Cl8N2Pd, orthorhombic, P212121 (no. 19), a = 16.5460(8) Å, b = 17.995(1) Å, c = 11.817(1) Å, V = 3518.5 Å3, Z = 4, Rgt(F) = 0.037, wRref(F2) = 0.099, T = 193 K.

GaN nanopillar and nanostripe arrays with embedded InGaN/GaN multi-quantum wells (MQWs) are fabricated by holographic lithography and subsequent reactive ion etching. Etch related damage of the nanostructures is successfully healed through annealing of NH3/N2 mixtures under optimized conditions.

Rotational Maker fringes were used to measure the non-linear susceptibilities chi[(super 2)(sub 31)] and chi[(super 2)(sub 33)] for a series of metalorganic chemical vapor deposition (MOCVD) and hydride vapor-phase epitaxy (HVPE) AlxGa1-xN thin-film samples grown on sapphire substrates. The results are consistent with theoretical studies of nonlinear susceptibilities for GaN and AlGaN.

The effect of subband gap illumination on transport properties of AIGaN/GaN heterostrcutures was investigated using the Shubnikov-de Haas and Hall effects.

A technique to fabricate monolithically integrated silicon solar cells is reported.

Results demonstrate that the thin AlGaN and thick GaN layers are coheretly strained as determined by x-ray diffraction map analysis. Data on mobility spectra reveal single-carrier transport at low temperatures.

Thin A1xGa1-xN layers grown by metalorganic chemical vapor deposition, were studied.

Experimental magnetic field dependent Hall and resistivity data is presented for two modulation-doped AlGaN/GaN heterostructures in the temperature range from 6 to 300 K and for a magnetic field up to 12 T. An analysis of the temperature dependencies of mobility and electron concentration in the GaN layer and two-dimensional electron gas indicates that electron transport in the GaN layer is dominated by carriers in the conduction band for the case of low-doping (10 super 18 per cu cm).

Two-dimensional reciprocal space mapping of high resolution x-ray diffraction was utilized to examine the structural properties of InGaN/GaN/AlGaN multiple quantum wells (MQW). It was found that the InGaN/GaN/AlGaN MQWs are grown coherently on the GaN base layer. Better interface properties were achieved with Si doping. Results indicated that Si doping in the GaN barriers influences the interface quality of the InGaN/GaN MQW systems.

Monoenergetic positron beam is used for probing the vacancy-type defects in AlN grown by metal-organic vapor phase epitaxy (MOVPE) and lateral epitaxial overgrowth (LEO) using halide vapor phase epitaxy. Doppler broadening spectra of the annihilation radiation are measured and compared to the spectra calculated by using the projector augmented-wave method.

Smooth N-polar InGaN/GaN and AlGaN/GaN multiquantum wells (MQWs) and heterostructures are grown by metal organic chemical vapor deposition on (0001) sapphire substrates with misorientation angles toward the a-sapphire angle. The studies have shown that the tendency toward formation of multiatomic steps at the film surface and at interfaces has increased with increasing misorientation angle.

The properties of GaN/[Al.sub.x][Ga.sub.1-x]N/GaN heterostructures with a different Al mole fraction and Si doping in the barrier layer and fabricated devices from selected wafers are examined. The fabricated devices have displayed a drain-source current of 0.9 A/mm at a gate-source voltage +1 V.

Smooth, high quality N-polar GaN films are grown by metal organic chemical vapor deposition (MOCVD) on misoriented sapphire substrates by using a high temperature nucleation process. The studies have shown that the quality of the N-polar GaN films deposited (0001) sapphire substrates with a misorientation angle is comparable to Ga-polar GaN-on-sapphire films grown in the same reactor.

The carrier capture dynamics and excitation dependent charge distributions of coupled InGaN/GaN multiple quantum well samples are examined. The results have shown a marked increase in the rate of carrier transfer to the single quantum well (SQW) region as the temperature increases.

The effect of isochronal thermal annealing on [super 60]Co gamma-irradiated Ni/n-GaN Schottky barrier diodes is examined. Isochronal thermal annealing at temperatures from 80 to 350 degree Celsius, performed following a low-temperature anneal was found to induce complete annihilation of radiation-induced defects

The stress relaxation of layers grown on nominally relaxed Al(sub 0.62)Ga(sub 0.38)N buffer layers on sapphire is reported. The results show that the threading dislocations in the Al(sub 0.49)Ga(sub 0.51)N layer inclined from the [0001] direction toward (1100) directions by ~15-25-degree.

The metalorganic chemical vapor deposition (MOCVD) growth and electrical characteristics of p-type nonpolar a-plane GaN and p-n junction diodes are examined. The electrical conductivity of the films revealed a strong dependence on the growth parameters.

Optical properties of dislocations in GaN epilayers are characterized by using cathodoluminecence technique combined with transmission electron microscopy (TEM-CL). The information of parameters such as carrier lifetime and diffusion length is obtained by the CL images simulation.

The presence of large polarization fields in the AlN barrier layer in AlN/GaN heterstructures results in high values of the two-dimensional electron gas (2DEG) sheet density of up to 3.6x10(super 13) cm(super -2). At room temperature, a combination of the high 2DEG sheet density of 2.15x10(super 13) cm(super -2) and high electron mobility of 1500 cm(super 2)/Vs in Al(sub 0.37)Ga(sub 0.63)N/AlN/GaN yielded a low sheet resistance value of 194 ohm.

A microscopic four-point probe (μ4PP) for resistivity measurements on thin films was designed and fabricated using the negative photoresist SU-8 as base material. The device consists of four microscopic cantilevers, each of them supporting a probe tip at the extremity. The high flexibility of SU-8 ensures a stable electrical point contact between samples and probe tip with all four electrodes even on rough surfaces. With the presented surface micromachining process, μ4PPs with a probe-to-probe spacing of 10–20 μm were fabricated. Resistivity measurements on thin Au, Al, and Pt films were performed successfully. The measured sheet resistances differ by less than 5% from those obtained by a commercial macroscopic resistivity meter. Due to the low contact forces (Fcont<10-4 N), the μ4PP is suitable to be applied also to fragile materials such as conducting polymers. Here the authors demonstrate the possibility of performing resistivity measurements on 100-nm-thick pentacene (C22H14) films with a sheet resistance Rs>106 Ω/□. [ABSTRACT FROM AUTHOR]

The authors have used positron annihilation spectroscopy and photoluminescence measurements to study the influence of silicon doping on vacancy formation in AlGaN:Si structures. The results show a correlation between the Doppler broadening measurements and the intensity from 510 nm photoluminescence transition. The reduction in the W parameter when the [Si]/[Al+Ga] fraction in the gas phase is above 3×10-4 indicates that the positrons annihilate in an environment where less Ga 3d electrons are present, i.e., they are trapped in group-III vacancies. The observation of vacancies at these silicon concentrations coincides with the onset of the photoluminescence transition at 510 nm. [ABSTRACT FROM AUTHOR]

Reprints a portion of the article 'AIN/GaN and (Al,Ga)/AIN/GaN two-dimensional electron gas structures grown by plasma-assisted molecular-beam epitaxy,' published in a 2002 issue of 'Applied Physics.'

Presents a correction to the article "Dopant Activation and Ultralow Resistance Ohmic Contacts to Si-ion-implanted GaN Using Pressurized Rapid Thermal Annealing," that was previously published in the 2004 issue of "Applied Physics Letters."