Defect Complexes and Non-Equilibrium Processes Underlying the P-Type Doping of GaN

It is well known that hydrogen plays a key role in p-type doping of GaN. It is believed that H passivates substitutional Mg during growth by forming a Mgs-N-Hi complex; in subsequent annealing, H is removed, resulting in p-type doping. Several open questions have remained, however, such as experimental evidence for other complexes involving Mg and H and difficulties in accounting for the relatively high-temperature anneal needed to remove H. We present first principles calculations in terms of which we show that the doping process is in fact significantly more complex. In particular, interstitial Mg plays a major role in limiting p-type doping. Overall, several substitutional/interstitial complexes form and can bind H, with vibrational frequencies that account for hitherto unidentified observed lines. We predict that these defects, which limit doping efficiency, can be eliminated by annealing in an atmosphere of H and N prior to the final anneal that removes H.

Defect Complexes and Non-Equilibrium Processes Underlying the P-Type Doping of GaN

It is well known that hydrogen plays a key role in p-type doping of GaN. It is believed that H passivates substitutional Mg during growth by forming a Mgs-N-Hi complex; in subsequent annealing, H is removed, resulting in p-type doping. Several open questions have remained, however, such as experimental evidence for other complexes involving Mg and H and difficulties in accounting for the relatively high-temperature anneal needed to remove H. We present first principles calculations in terms of which we show that the doping process is in fact significantly more complex. In particular, interstitial Mg plays a major role in limiting p-type doping. Overall, several substitutional/interstitial complexes form and can bind H, with vibrational frequencies that account for hitherto unidentified observed lines. We predict that these defects, which limit doping efficiency, can be eliminated by annealing in an atmosphere of H and N prior to the final anneal that removes H.

The Influence of Thin Nickel Coatings on the Goss-Texture Development in Iron–3% Silicon

Microstructure and texture (ODF) investigations were carried out on Fe–3% Si electrical steels with different C, MnS and AlN content (CGO and HGO quality). The main result was that by a thin (0.25 μm) Ni layer on the sheet surfaces produced by electroplating before the final anneal the starting temperature of discontinuous grain growth could be decreased and the Goss texture could be sharpened. This effect was influenced by the heating rate and disappeared after decarburization. It is caused by the diffusion of Ni along the grain boundaries by which the segregation and precipitation characteristics of elements like C, N, S, is changed.

CMI-C MAGNETIC IRON

CMI-C Magnetic Iron is a low-carbon magnetic iron especially processed with a critical strain for optimum uniformity. Maximum magnetic properties are achieved following suggested final anneal applied to fabricated parts. Its applications include electromagnet cores, plungers and pole pieces; generator and motor field frames; magnetic chucks; and chuck plates. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Fe-75. Producer or source: Connecticut Metals Incorporated.

Fabrication and Annealing Factors Affecting Grain Size of 18Cr8Ni-Ti Superheater Materials in Steam Boilers

The effect of cold deformations as encountered in tube and superheater fabrication and of temperature and time of annealing on the grain-size characteristics of 18Cr8Ni-Ti is demonstrated by laboratory experiments with material from six heats of steel. It is shown that cold-drawn tubing retains a relatively uniform small grain size at annealing temperatures up to about 1900 F to 1950 F and that above this temperature individual grains begin to grow at an accelerated rate, leading to a mixed grain-size structure. Annealing times between 5 and 15 minutes caused only insignificant differences in the over all grain size, but extension of exposure to 30 minutes produced a noticeably larger grain structure. Small cold deformations as may be introduced into the material by tube straightening can, when followed by a final anneal, cause excessive localized grain enlargements. Observations pointed to the possibility that materials with high Ti/C ratios may retain a predominantly small grain size at annealing temperatures as high as 2050 F.