Phase separation in InGaN multiple quantum wells annealed at high nitrogen pressures

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Abstract
Phase separation was found to occur in In 0.33 Ga 0.67 N/GaN multiple-quantum-well structures after annealing at 975 °C in a hydrostaticpressure of 5 kbar N 2 for 4 h. X-ray diffraction(XRD)spectra of the as-grown samples showed superlattice peaks that were replaced by a broad, single-phase peak after annealing.Transmission electron microscopy(TEM) images of the annealed samples show In-rich precipitates and voids that are found only within the quantum-well region. Both TEM and XRD measurements indicated that the formation of voids and second phases were suppressed after annealing in a hydrostaticpressure of 15 kbar. In addition, optical absorption measurements on these samples showed no indication of a peak at 2.65 eV that was observed in previous annealing studies.