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Feeding costs represent one of the highest expenditures in animal production systems. Breeding efficient animals that express their growth potential while eating less is therefore a major objective for breeders. We estimated the genetic parameters for feed intake, feed efficiency traits (residual feed intake (RFI) and feed conversion ratio (FCR)), growth and body composition traits in the Romane meat sheep breed. In these traits, selection responses to single-generation divergent selection on RFI were evaluated. From 2009 to 2016, a total of 951 male lambs were tested for 8 weeks starting from 3 months of age. They were weighed at the beginning and at the end of the testing period. Backfat thickness and muscle depth were recorded at the end of the testing period through ultrasound measurements. Feed intake was continuously recorded over the testing period using the automatic concentrate feeders. The heritability of RFI was estimated at 0.45 ± 0.08, which was higher than the heritability of FCR (0.30 ± 0.08). No significant genetic correlations were observed between RFI and growth traits. A favourable low negative genetic correlation was estimated between RFI and muscle depth (−0.30 ± 0.15), though additional data are needed to confirm these results. The selection of low RFI sires based on their breeding values led to the production of lambs eating significantly less concentrate (3% decrease in the average daily feed intake), but with the same growth as lambs from sires selected based on high RFI breeding values. We concluded that in meat sheep, RFI is a heritable trait that is genetically independent of post-weaning growth and body composition traits. A one-generation divergent selection based on RFI breeding values highlighted that substantial gains in feeding costs can be expected in selection schemes for meat sheep breeds. [ABSTRACT FROM AUTHOR]

This paper describes an extensive analysis of the role of off-state and semi-on state bias in inducing the trapping in GaN-based power High Electron Mobility Transistors. The study is based on combined pulsed characterization and on-resistance transient measurements. We demonstrate that--by changing the quiescent bias point from the off-state to the semi-on state--it is possible to separately analyze two relevant trapping mechanisms: (i) the trapping of electrons in the gate-drain access region, activated by the exposure to high drain bias in the off-state; (ii) the trapping of hot-electrons within the AlGaN barrier or the gate insulator, which occurs when the devices are operated in the semi-on state. The dependence of these two mechanisms on the bias conditions and on temperature, and the properties (activation energy and cross section) of the related traps are described in the text. [ABSTRACT FROM AUTHOR]

AlGaN/GaN heterostructure field effect transistors with a 150 nm thick GaN channel within stacked AlxGa1-xN layers were investigated using Raman thermography. By fitting a thermal simulation to the measured temperatures, the thermal conductivity of the GaN channel was determined to be 60 W m-1 K-1, over 50% less than typical GaN epilayers, causing an increased peak channel temperature. This agrees with a nanoscale model. A low thermal conductivity AlGaN buffer means the GaN spreads heat; its properties are important for device thermal characteristics. When designing power devices with thin GaN layers, as well as electrical considerations, the reduced channel thermal conductivity must be considered. [ABSTRACT FROM AUTHOR]

In this paper, we report on the challenges related to growth and processing of 200 mm GaN-on-Si wafers in a CMOS fab. We describe the Au free process we developed as well as how we assure wafer quality prior processing. For the first time, we analyze possible Ga contamination issues related to the processing of GaN wafers and we present the cleaning procedures we developed to avoid it. [ABSTRACT FROM AUTHOR]

Abstract: In this work we report on the two most common failure modes for AlGaN/GaN-based HEMTs: the gate leakage increase and the output current drop. First, by performing step-stress experiments in function of the step-time (t STEP) we show that the critical voltage for the increase of gate leakage current depends on the t STEP and is not associated with a permanent drop of the output current. Consequently, identification of the critical voltage by means of step-stress is not meaningful per se since it depends on the t STEP used. Second, we show that during high power stress at high voltage a permanent output current drop occurs. The failure analysis reveals the formation of crystallographic defects in the AlGaN layer along the whole width of the gate, in agreement with the inverse piezoelectric theory. However, in contrast to the degradation model based on the inverse piezoelectric effect, these defects do not aid the leakage of electrons from the gate toward the drain electrode since the output current drop is not associated with an increase of the gate leakage current. Therefore, combining the outcome of the two experiments, we suggest that the two most common failure modes are not correlated despite both might concur to the device degradation. Finally, an excellent stability is shown for devices with reduced Al content in the AlGaN barrier, highlighting the fundamental role of strain on reliability of AlGaN/GaN-based devices. [Copyright &y& Elsevier]

Abstract: In this work, the impact of 1000h thermal storage test at 325°C on the performance of gallium nitride high electron mobility transistors grown on Si substrates (GaN-on-Si HEMTs) is investigated. The extensive DC- and pulse-characterization performed before, during and after the stress did not reveal degradation on the channel conduction properties as well as formation of additional trapping states. The failure investigation has shown that only the gate and drain leakage currents were strongly affected by the high temperature storage test. The physical failure analysis revealed a Au inter-diffusion phenomenon with Ni at the gate level, resulting in a worsening of the gate–AlGaN interface. It is speculated that this phenomenon is at the origin of the gate and drain leakage current increasing. [Copyright &y& Elsevier]

The common practice of artificially rearing lambs from prolific meat breeds of sheep constitutes a welfare issue due to increased mortality rates and negative health issues. In this multidisciplinary study, we investigated the possible short- and mid-term advantages of artificially feeding fresh ewe's milk instead of commercial milk replacer on lambs' growth, health and welfare. Romane lambs were either separated from their mothers on D3 and fed with Lacaune ewes' milk (LAC , n = 13) or milk replacer (REP , n = 15), or they were reared by their mothers (MOT , n = 15). On D45, they were weaned, gathered in single-sex groups until the end of the study on D150. Lamb performance and biomarkers of overall health were assessed by measuring: growth, dirtiness of the perianal area, enteric pathogens in the faeces, total antioxidant status and redox status assessed by plasma reduced glutathione/oxidised glutathione ratio, and immune response after vaccination against chlamydiosis. As an exploratory approach, blood cell transcriptomic profiles were also investigated. Last, qualitative behaviour assessment (QBA) was performed as an integrated welfare criterion. Lacaune ewes' milk and REP never differed in their average daily gain but grew less than MOT lambs in the early suckling period and just after weaning. No effect was detected afterwards. On D30, LAC and REP lambs had lower total antioxidant and higher redox status than MOT lambs but did not differ among themselves. Lacaune ewes' milk and MOT had a cleaner perianal area than REP lambs on D21, while faecal pathogen infection did not vary between the treatment groups. After vaccination, LAC also had a stronger immune response on D90 compared to REP lambs. Transcriptome analysis performed on D150 showed differential gene expression, mainly in relation to inflammatory, immune and cell cycle response, between male lambs of the LAC group and those of the MOT and REP groups. Based on QBA, LAC lambs never differed from MOT lambs in their general activity and varied from REP only on D21; REP lambs were always more agitated than MOT lambs. In conclusion, artificial milk feeding impaired early growth rate, health and emotional state mainly during the milk feeding period and at weaning. Feeding artificially reared lambs with fresh ewe's milk partly mitigated some of the negative effects induced by milk replacer but without achieving the full benefit of being reared by the mother. [ABSTRACT FROM AUTHOR]

A novel normally-off AIN/GaN metal-oxide-semiconductor high electron mobility transistors (MOSHEMT) on 100-mm Si substrates for high-power applications is demonstrated for the first time by means of a selective thermal oxidation of AIN. The formation of a high-quality insulating AION layer resulting from the dry thermal oxidation of AIN at 900 ° C in oxygen has been identified by transmission electron microscopy and X-ray photoelectron spectroscopy. The AIN thermal oxidation appears to be highly selective toward the SiN cap layer allowing the local depletion of the 2-D electron gas (self-aligned to the gate) and thus the achievement of normally-off operation. Threshold voltage (VT) of +0.8 V and drain leakage current at VGS = 0 V well below 1 µA/mm are obtained reproducibly over the wafer. The comparison of the fabricated MOSHEMTs with the control sample (identical but nonoxidized) reveals a drastic shift of VT toward positive values and three to four orders of magnitude drain leakage current reduction. [ABSTRACT FROM AUTHOR]

Ultrathin-barrier normally off AIN/GaN/A1GaN double-heterostructure field-effect transistors using an in situ SiN cap layer have been fabricated on 100-mm Si substrates for the first time. The high 2DEG density in combination with an extremely thin barrier layer leads to enhancement-mode devices with state-of-the-art combination of specific ON-resistance that is as low as 1.25 mπ · cm2 and breakdown voltage of 580 V at VGS = 0 V. Despite the 2-μm gate length used, the transconductance peaks above 300 mS/mm. Furthermore, pulsed measurements show that the devices are dispersion free up to high drain voltage VDS = 50 V. More than 200 devices have been characterized in order to confirm the reproducibility of the results. [ABSTRACT FROM AUTHOR]

Abstract: Properties of stress-induced percolation paths in AlGaN in step-stressed AlGaN/GaN high electron mobility transistors are investigated in details. DC and transient gate and drain current analysis are combined with low frequency noise and electroluminescence measurements. The observation of random telegraph signal (RTS) noise with large relative amplitude indicates that RTS is due to modulation of gate current in the percolation path by action of single defects. Measurements of RTS amplitude as a function of forward or reverse gate voltage can reveal masked gate leakage current components related to individual percolation paths. The observed gradual increase in forward gate current ideality factor with progressing stress, indicating defect penetration inside the percolation path in AlGaN, is explained by a simple model. The role of slow trapping in the modulation of current in the percolation path is discussed too. [Copyright &y& Elsevier]