Growth study of chemical beam epitaxy of GaNxP1−x using NH3 and tertiarybutylphosphine
Abstract A study in the growth of GaN x P 1 − x epilayers by chemical beam epitaxy using tertiarybutylphosphine (TBP), ammonia (NH 3 ), and elemental Ga or triethylgallium is reported. Monitoring reflection high-energy electron diffraction (RHEED) intensity oscillations, we observe that both group-III- and group-V-induced incorporation rates are increased when NH 3 is introduced into a single cracker with TBP. From the difference in the periods of group-V-induced RHEED intensity oscillations, a 16% N incorporation is expected, but X-ray rocking curve measurement shows only 0.08% N. Using separate TBP and NH 3 crackers results in no enhancement in incorporation rates. We conclude that the cracking efficiency of TBP is increased with NH 3 co-injection.
Metalorganic chemical vapor deposition of GaInNAs lattice matched to GaAs for long-wavelength laser diodes
Abstract The crystal growth of GaInNAs lattice matched to GaAs by metalorganic chemical vapor deposition using dimethylhydrazine as the nitrogen source is described for realizing long-wavelength laser diodes. It was found that the crystalline quality of GaInNAs on AlGaAs is improved by inserting a GaAs spacer layer between GaInNAs and AlGaAs. The photoluminescence spectra of GaAs/Ga 0.9 In 0.1 N y As 1− y /GaAs-DH was measured at room temperature with N content y of 1.5, 2.3 and 2.9%, respectively. The PL intensity decreases with increasing N content, though the lattice mismatch of GaInNAs layers to GaAs substrates decreases with increasing N content. We also produced the laser diodes with GaInNAs active layer and measured the N content dependence of the threshold current density. With increasing N content, the threshold current density increases with the reduction of PL intensity. We made it clear that GaInNAs material system is applicable to a 1.3 μm laser diode on a GaAs substrate. We expect to achieve a good lasing performance at 1.3 μm with the most suitable growth condition and design of laser diodes.
Hutcheson's Moral Sense Theory Reconsidered
There is no more central feature of Francis Hutcheson's moral philosophy than his theory of the moral sense. In the past this sense or faculty was widely understood to be a distinctive and independent sense devoted to the apprehension of moral qualities, but William Frankena has in recent years challenged this traditional view of Hutcheson's theory, and offered in its place an emotivist interpretation. Without question Frankena's study was of the first importance, in that it seems to have overturned the much too simplistic traditional view of the moral sense. Unfortunately, however, Frankena's own interpretation of the moral sense is as inadequate and misleading as the view he overturns, for he concludes that the moral sense is not at all a cognitive faculty, that it does not, that is, apprehend moral qualities, but, rather, is a faculty that enables and motivates us to feel, express, and evoke moral emotions. The moral sense, he argues, is “the source of the feelings involved” in moral approbation or disapprobation, and this approbation is “wholly non-cognitive, very much as it is on Ayer's more recent [emotivist] view … This, I shall show, is much too narrow a view; Hutcheson did not limit the moral sense to a single function, nor did he — lacking as he did twentieth-century perspectives — find it either necessary or desirable to assume that the domains of the cognitive and the emotive (or affective) were mutually exclusive.