Microstructure of non-polar GaN on LiGaO2 grown by plasma-assisted MBE
We have investigated the structure of non-polar GaN, both on the M - and A-plane, grown on LiGaO2 by plasma-assisted molecular beam epitaxy. The epitaxial relationship and the microstructure of the GaN films are investigated by transmission electron microscopy (TEM). The already reported epi-taxial relationship and for M -plane GaN is confirmed. The main defects are threading dislocations and stacking faults in both samples. For the M -plane sample, the density of threading dislocations is around 1 × 1011 cm-2 and the stacking fault density amounts to approximately 2 × 105 cm-1. In the A-plane sample, a threading dislocation density in the same order was found, while the stacking fault density is much lower than in the M -plane sample.
GaN grown in polar and non-polar directions
In this paper, defects formed in GaN grown by different methods are reviewed. Thin GaN films were grown on c-, m-, and a-planes on a number of substrates and typical defects as characterized by transmission electron microscopy are described. For polar epilayers grown on c-plane sapphire the typical defects are dislocations (edge, screw and mixed). The lowest dislocation density was obtained for homoepitaxial growth using molecular beam epitaxy (MBE) or hydride vapour phase epitaxy (HVPE). In these cases, the core structure of screw dislocations were studied in detail. In both cases, the cores are full. In the layers grown by HVPE the dislocations are decorated by pinholes stacked on top of each other. These pinholes are empty inside and their formation is attributed to impurities (oxygen) present in these layers. In these layers Ga-rich cores have been found. These were not observed in the layers grown by MBE on the top of the HVPE templates. Epilayers grown in non-polar directions (m- or a-plane) have a high density of planar defects (stacking faults) terminated by partial dislocations. Only low energy faults were found. The majority of these faults are formed at the interface with the substrate and propagate to the sample surface.
Clinical chemical values and variations in Rasa Aragonesa ewes and lambs
Reference values of biochemical parameters in serum of Rasa Aragonesa ewes and their physiological variations were determined. Total proteins were 53.0–80.0 g/l, glucose 2.17–5.13 mmol/l, cholesterol 0.83–2.31 mmol/l, total bilirubin 1.85–6.49 μmol/l, urea 3.15–10.39 mmol/l, GGT 36–93 U/l (37°C), ALAT 11–33 U/l (37°C) and ASAT 71–209 U/l (37°C). Ewes were divided into three groups: A, 1- and 2-year-old ewes; B, ewes 3 and 4 years old; C, older ewes. Age had significant influence (P<0.05) on ASAT only during pregnancy, with higher levels for younger ewes. Blood parameters in lambs were determined at 5–10 d of life (nursing), 25 to 30 d of life receiving their mother's milk and 80–90 g of feed; and 45 to 50 d of life, weaned, receiving only solid feed. Serum urea and ALAT tended to increase with age, whereas total protein, globulins, cholesterol and GGT decreased with age. These values are of practical importance in the diagnosis of diseases and metabolic disorders in Rasa Aragonesa ewes and lambs under field conditions.