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Using scattering to improve light extraction from semiconductors is a widely adopted method to increase the efficiency of modern light-emitting devices. Recently, there has also been much interest in the potential emission enhancement provided by the strong coupling between surface plasmons and semiconductor emitters. In this study, we develop a Green’s function-based model to describe the emission enhancement and modification in optical properties obtained as a result of scattering and plasmon engineering. The Green’s function method is used to answer fundamental questions regarding luminescence enhancement in periodically grated GaN light-emitting structures. The Green’s function approach is a very attractive analytical method to studying the emission properties of grated multilayer structures, providing insight beyond numerical solutions. Modeling results from reflectometry measurements of silver-grated GaN structures allows to explain experimentally observed interference features. A discussion regarding the role of periodic grating in enhancing emission from the structures is included. [ABSTRACT FROM PUBLISHER]

We report a new phenomenon relatedto Al-induced carrier confinementat the interface in core–shell GaAs/AlxGa1–xAs nanowires grownusing metal–organic vapor phase epitaxy with Au as catalyst.All AlxGa1–xAs shells strongly passivated the GaAs nanowires, but surprisinglythe peak photoluminescence (PL) position and the intensity from thecore were found to be a strong function of Al composition in the shellat low temperatures. Large and systematic red shifts of up to ∼66nm and broadening in the PL emission from the GaAs core were observedwhen the Al composition in the shell exceeded 3%. On the contrary,the phenomenon was observed to be considerably weaker at the roomtemperature. Cross-sectional transmission electron microscopy revealsAl segregation in the shell along six Al-rich radial bands displayinga 3-fold symmetry. Time-resolved PL measurements suggest the presenceof indirect electron–hole transitions at the interface at higherAl composition. We discuss all possibilities including a simple shell–core–shellmodel using simulations where the density of interface traps increaseswith the Al content, thus creating a strong local electron confinement.The carrier confinement at the interface is most likely related toAl inhomogeneity and/or Al-induced traps. Our results suggest thata low Al composition in the shell is desirable in order to achieveideal passivation in GaAs nanowires. [ABSTRACT FROM AUTHOR]

Carrier lifetimes of the recombination processes in light emitting diodes (LEDs) depend strongly on the operating point. We measure the carrier lifetimes of InGaN/GaN LEDs at low current densities by applying the differential carrier lifetime analysis. In the measurement setup the LED is driven with constant current modulated with small amplitude alternating current (AC) and the carrier lifetime is obtained from the phase difference between input AC and light output. In addition to the optical method, we also extract the lifetimes directly from the capacitance and differential resistance of the LED obtained using an impedance analyzer and compare the results to lifetimes obtained by the optical setup. The carrier lifetimes were found to increase from hundreds of nanoseconds to microseconds when the current density was decreased from tens of A/cm2 to tens of mA/cm2. Both measurement methods resulted in similar lifetimes (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We have derived a quantum trajectory model for describing the dynamics of cavity fields of optoelectronic devices. We apply the model to describe the photon statistics of semiconductor devices. The model is based on three parameters: the injected current, the electron-photon coupling in semiconductor active material, and the cavity loss rate. The model can be applied to solve the steady state photon statistics of various device configurations and also describe the transient phenomena. We show that depending on the parameters the device can operate e.g. as a light emitting diode or as a laser. We also investigate the photon correlation properties and discuss the photon bunching and anti-bunching phenomena. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]