Coherent In0.25Ga0.75As quantum dots (QDs) are realized on GaP(001) substrates by metalorganic vapor phase epitaxy in the Stranski-Krastanow mode utilizing a thin GaAs interlayer prior to In0.25Ga0.75As deposition. Luminescence is observed between 2.0 eV and 1.83 eV, depending on the thickness of the In0.25Ga0.75As layer. The critical thickness for the two-dimensional to three-dimensional transition of the layer is determined to 0.75 to 1.0 monolayers. A mean activation energy of 489 meV for holes captured by In0.25Ga0.75As quantum dots is measured by deep-level transient spectroscopy, yielding a hole storage time of 3 µs at room temperature.

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Fourier transform infrared absorption measurements have been carried out on GaAs crystals doped or implanted with carbon, nitrogen and oxygen. In the presence of carbon and nitrogen, thermally stable defects occur with strong molecular-like bonding giving rise to absorption bands of vibrational character in the mid-infrared. By implantation of the nitrogen isotopes 14N and 15N, a complex of the chemical composition CN2 is identified. This defect is the origin for the mode at 2060 cm−1 previously attributed to a (C, O)-complex. A further absorption band at 1973 cm−1 is tentatively attributed to the stretching mode of a CN entity

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The GaAs vertical gradient freeze (VGF) crystal growth process can be intensified in various ways, e.g., utilizing external fields, scaling up, numbering up the crucibles, etc. Successful application of traveling magnetic fields (TMFs) in 4 in. VGF GaAs growth for the flow control and process acceleration encouraged us to search for synergistic conceptions. Pros and cons of process scale up and numbering up under TMFs were addressed using threedimensional numerical simulations. The comparison of concepts was focused on the control of solid/liquid interface morphology and energy balance. A novel multicrucible furnace design was proposed and compared with a single-crucible design, both based on KRISTMAG technology. The simulation results showed the clear superiority of the numbering-up concept; e.g., the total energy consumption per run with equal yield was reduced to 32% of the value for the standard process. Moreover, a beneficial interface morphology was achievable without a trade-off with growth rates.