A room temperature polariton condensate realized in a microcavity with embedded GaN quantum wells emits linearly polarized light at threshold with the plane of polarization pinned to one of the crystallographic axes. With increasing pumping power, a depinning of the polarization is observed resulting in a progressive decrease of the polarization degree of the emitted light. This depinning is understood in terms of polariton-polariton repulsion competing with the static disorder potential effect. The polarization behavior differs from that of conventional lasers where the polarization degree usually increases as a function of pumping power.

The heterointerface IV curves at different intensity illumination levels have been extracted from full IV curves of triple-junction GaInP/GaAs/Ge solar cell. For this purpose a special approach for multi-junction solar cells has been proposed. The solar cell equivalent circuit consisting of two parts-generation and connecting ones were considered. The generation part includes all photovoltaic p-n junctions, while connecting one incudes a resistance of the layers, spreading resistance, tunnel diodes and heterointerfaces. The equivalent circuit was used for analysis of «kink» free IV curves of Ge and GaAs solar cells. In this case the IV curves of connecting part are completely described by the spreading resistance. The analysis of GaInP/GaAs/Ge allows to obtain heterointerface IV curves and it has been shown that their shape depends on illumination level. The empirical formula was used for an approximation of heterointerface IV curves to show the nature of current flow mechanism which was established as tunneling one.

We demonstrate amber-green emission from AlxIn1–xP light-emitting diodes (LEDs) with luminescence peaked at 566 nm and 600 nm. The LEDs are metamorphically grown on GaAs substrates via a graded InyGa1–yAs buffer layer and feature electron confinement based on the control of AlxIn1–xP CuPt atomic ordering. A control sample fabricated without order-disorder carrier confinement is used to illustrate device improvement up to a factor of 3 in light output due to confinement at drive currents of 40 A/cm2. The light output at room temperature from our AlxIn1–xP LED structure emitting at 600 nm is 39% as bright as a GaxIn1–xP LED emitting at 650 nm.

Articles you may be interested inEffects of doping and grading slope on surface and structure of metamorphic InGaAs buffers on GaAs substrates Direct-bandgap InAlP alloy has the potential to be an active material in nitride-free yellow-green and amber optoelectronics with applications in solid-state lighting, display devices, and multi-junction solar cells. We report on the growth of high-quality direct-bandgap InAlP on relaxed InGaAs graded buffers with low threading dislocation densities. Structural characterization reveals phase-separated microstructures in these films which have an impact on the luminescence spectrum. While similar to InGaP in many ways, the greater tendency for phase separation in InAlP leads to the simultaneous occurrence of compositional inhomogeneity and CuPt-B ordering. Mechanisms connecting these two structural parameters are presented as well as results on the effect of silicon and zinc dopants on homogenizing the microstructure. Spontaneous formation of tilted planes of phase-separated material, with alternating degrees of ordering, is observed when InAlP is grown on vicinal substrates. The photoluminescence peak-widths of these films are actually narrower than those grown on exact (001) substrates. We find that, despite phase-separation, ordered direct-bandgap InAlP is a suitable material for optoelectronics. V C 2013 AIP Publishing LLC.