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Comparable microcavities with 3λ/2 (∼240 nm) active regions containing distributed (In,Ga)N quantum wells, grown on GaN substrates and bounded by two dielectric mirrors, have been fabricated by two different routes: one using laser lift-off to process structures grown on GaN-on-sapphire templates and the second using freestanding GaN substrates, which are initially processed by mechanical thinning. Both exploit the properties of an Al0.83In0.17N layer, lattice matched to the GaN substrate and spacer layers. In both cases cavity quality factors >400 are demonstrated by measurements of the cavity-filtered room-temperature excitonic emission near 410 nm. [ABSTRACT FROM AUTHOR]

The authors report the temperature dependent photoluminescence characteristics of a series of GaInNAsSb/Ga(N)As double quantum wells which all emit at 1.5–1.55 μm at room temperature and whose design is such that the quantum wells have nominally identical valence band profiles but show different confinement depth in the conduction band. The photoluminescence quenching at high temperature demonstrates a thermal activation energy independent of the conduction band offset and can be most plausibly attributed to the unipolar thermalization of holes from the quantum wells to the barriers. This effect will intrinsically limit the flexibility of heterostructure design using GaInNAs(Sb), as it would for any other material system with small valence band offset. [ABSTRACT FROM AUTHOR]

High-quality GaInN(Sb)As/GaNAs double quantum wells (QWs) which emit at 1.54 μm wavelength at room temperature with a narrow linewidth of ∼34 meV (12 meV at 5 K) were fabricated by molecular-beam epitaxy on GaAs substrates. Photoluminescence and photoluminescence excitation spectroscopy were used to study the electronic states and optical properties of these heterostructures. By characterizing samples grown using different fluxes of Sb, the role played by Sb in the growth process and optical properties was elucidated. At low Sb flux, Sb atoms act mainly as a surfactant which improves the microstructure of the QWs and enhances the photoluminescence intensity. With an increase of Sb flux, some of the Sb atoms may incorporate into GaInNAs to form a quinary compound. In the latter case, the incorporation of Sb could also enhance the N composition in the QWs, which may be responsible for the further reduction of the band gap. [ABSTRACT FROM AUTHOR]

We report the temperature-dependent photoluminescence characterization of InNxAs1-x/In0.53Ga0.47As/InP multiple quantum wells with various N contents emitting in the midinfrared wavelength range. The emission wavelength in this material system can be tuned by the N content, but the bowing effect is much weaker than in GaNAs. The correlation between the optical properties and the interface quality is demonstrated by examining the barrier-related emission. The role played by N is elucidated by comparing quantum well samples having either zero, low (0.25%) or high (5%) N content. [ABSTRACT FROM AUTHOR]

We report optical studies of high-quality 1.3 μm strain-compensated GaInNAs/GaAs single-quantum-well structures grown by metalorganic vapor phase epitaxy. Photoluminescence excitation (PLE) spectroscopy shows clearly the electronic structure of the two-dimensional quantum well. The transition energies between quantized states of the electrons and holes are in agreement with theoretical calculations based on the band anti-crossing model in which the localized N states interact with the extended states in the conduction band. We also investigated the polarization properties of the luminescence by polarized edge-emission measurements. Luminescence bands with different polarization characters arising from the electron to heavy-hole and light-hole transitions, respectively, have been identified and verify the transition assignment observed in the PLE spectrum. [ABSTRACT FROM AUTHOR]

The electrical and optical characteristics of a 370 nm AlGaN light-emitting diode based on a microring geometry is presented. By structuring the light emission area into an interconnected array of microscale rings, current spreading in the n-type cladding layers is improved. A reduction of differential series resistance is observed, and the device saturates at a higher current as the carriers are injected efficiently and uniformly across the junction areas. As a result, optical output power from the microring light-emitting diode is improved compared to a conventional device of broad area geometry. [ABSTRACT FROM AUTHOR]

A technique based on the Fresnel diffraction effect for the fabrication of nano-scale site-controlled ring structures in InGaN/GaN multi-quantum well structures has been demonstrated. The ring structures have an internal diameter of 500 nm and a wall width of 300 nm. A 1 cm-1 Raman shift has been measured, signifying substantial strain relaxation from the fabricated structure. The 9 nm blueshift observed in the cathodoluminescence spectra can be attributed to band filling and/or screening of the piezoelectric field. A light emitting diode based on this geometry has been demonstrated. [ABSTRACT FROM AUTHOR]

We report on the nitrogen-concentration dependence of optical transitions between quantized states of electrons and holes in GaInNAs/GaAs multi-quantum wells. Using low-temperature photoluminescence excitation spectroscopy, systematic studies have been performed on a series of samples with nitrogen concentrations in the range 0%-1.14%. The observed data were compared with theoretical fitting based on the band anticrossing model in which the localized N states interact with the extended states in the conduction band, taking strain effects into account. Our results are consistent with the band anticrossing model, but with differing coupling strength between different quantum states of electrons in the quantum wells. [ABSTRACT FROM AUTHOR]