The amount of carbon in GaAs and (Al,Ga)As films depends on the orientation of crystals grown by metalorganic chemical vapor deposition. We investigated the relation between the incorporation of carbon and the orientation of crystals using (100), (311)A, and (311)B substrates. The concentration of electrons on (311)B substrates of unintentionally doped films was higher than those of the films on (100) and (311)A substrates. The films grown on (311)B substrates did not show p-type behavior even when they were grown with a fairly low V/III ratio. The relative intensity of the free-to-carbon acceptor luminescence of the films grown on (311)B substrates was smaller than that of films grown on the other substrates. This is consistent with the results of carbon contamination indicated by secondary ion mass spectra. Furthermore, a reduced peak in photoluminescence caused by defects was observed when (311)B substrates were used.
Hot spring waters in Shimogamo, Izu Peninsula, Japan, were analyzed for the stable isotopes of boron as well as for chemical compositions. The boron isotopic ratios, "B/10B, of the waters range from 4.190 to 4.216, corresponding to the variation in &'IB from + 36.2 to + 42.6 permil. These values are very high compared to those of hot spring waters in other areas on the Japanese islands and close to that of sea water. The results of the isotopic and chemical analyses indicate that the Shimogamo hot spr ing waters are mixtures of surface water and a deep geothermal brine directly derived from sea water through the interaction with heated silicate rocks.
Photoluminescence and electrical studies of Sidoped Al x Ga1−x As grown on various substrate orientations by metalorganic chemical vapor deposition J. Appl. Phys. 69, 3278 (1991); 10.1063/1.348548 Resonant tunneling in GaAs/AlAs heterostructures grown by metalorganic chemical vapor deposition Appl. Phys. Lett. 46, 285 (1985); 10.1063/1.95660
Photoluminescence of AlGaAs/GaAs quantum wells grown by metalorganic chemical vapor depositionThe interface of a GaAsl Alx Gal ~ x As heterostructure grown by metalorganic chemical vapor deposition has been studied by photoluminescence spectroscopy by using a step-etching technique. Luminescence peaks associated with vacancy complexes emitted from both GaAs and Alx Gal __ x As layers were observed, and these peaks were remarkably intense on both sides of the GaAsl A!x Gal __ x As interface region. This result can be explained by the accumulation of vacancies in the interface region. The cause of this vacancy accumulation at the interface is discussed.
Photoluminescence at various temperatures of highly doped (5×1017 cm−3) Al0.3Ga0.7As grown by molecular-beam epitaxy has been studied. A luminescence peak at about 100 meV below the edge emission was observed. The intensity of this peak decreases as the As4/(Ga+Al) flux ratio increases for p-type samples, but decreases for n-type samples. An analysis based on the configurational coordinate model suggests that the origin of the luminescence may be a vacancy-dopant complex which acts as a nonradiative center at room temperature, as the intensity of the peak is inversely proportional to the intensity of the edge emission at room temperature.
Degradation of GaAs/AlGaAs double-heterostructure light-emitting diodes under accelerated aging tests has been investigated through cathodoluminescence measurements. We observed an increase in intensity of the band-edge emission and a decrease in that of defect-related deep level emision for the cladding layers. As for the active layer, a decrease was observed in the intensity of the band-edge emission. These results suggest that defects migrate gradually from the cladding layer into the active layer.
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