Increasing the quantum efficiency of InAs/GaAs QD arrays for solar cells grown by MOVPE without using strain-balance technology

Research into the formation of InAs quantum dots (QDs) in GaAs using the metalorganic vapor phase epitaxy technique ispresented. This technique is deemed to be cheaper than the more often used and studied molecular beam epitaxy. The bestconditions for obtaining a high photoluminescence response, indicating a good material quality, have been found among awide range of possibilities. Solar cells with an excellent quantum ef?ciency have been obtained, with a sub-bandgapphoto-response of 0.07 mA/cm2per QD layer, the highest achieved so far with the InAs/GaAs system, proving the potentialof this technology to be able to increase the ef?ciency of lattice-matched multi-junction solar cells and contributing to abetter understanding of QD technology toward the achievement of practical intermediate-band solar cells

Highly temperature-stable modulation characteristics of multioxide-aperture high-speed 980 nm vertical cavity surface emitting lasers

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 97, 151101 (2010) and may be found at https://doi.org/10.1063/1.3499361.We present multioxide-aperture 980 nm-range vertical cavity surface emitting lasers (VCSELs) with highly temperature stable modulation characteristics operating error-free at 25 Gbit/s at 25 and 85°C. We perform small signal modulation experiments and extract the fundamental physical parameters including relaxation resonance frequency, damping factor, parasitic cut-off frequency, -factor, and -factor, leading to identification of thermal processes and damping as the main factors that presently limit high speed device operation. We obtain very temperature-insensitive bandwidths around 13–15 GHz. Presented results clearly demonstrate the suitability of our VCSELs for practical and reliable optical data transmission systems.EC/FP7/224211/EU/VISIT - Vertically Integrated Systems for Information Transfer/VISITDFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement

Near field scanning optical microscopy for investigation of high power semiconductor lasers

В данной работе были исследованы карты распределения ближнего поля InGaAs/GaAs/AlGaAs полосковых инжекционных лазеров при различных токах накачки. Было показано, что в структурах, состоящих из двух резонансно связанных волноводов, наблюдается подавление мод высоких порядков.Near field intensity distributions of InGaAs/GaAs/AlGaAs lasers including broadened waveguides based on coupled large optical cavity (CLOC) structures were investigated. It was demonstrated that scanning near field optical microscopy gives direct proof of suppressing the transverse high-order mode lasing.Работа выполнена при поддержке РНФ (соглашение № 14-42-00006-П

Room-temperature yellow-orange (In,Ga,Al)P–GaP laser diodes grown on (n11) GaAs substrates

We report room temperature injection lasing in the yellow–orange spectral range (599–605 nm) in (AlxGa1–x)0.5In0.5P–GaAs diodes with 4 layers of tensile-strained InyGa1–yP quantum dot-like insertions. The wafers were grown by metal–organic vapor phase epitaxy side-by-side on (811), (211) and (322) GaAs substrates tilted towards the direction with respect to the (100) surface. Four sheets of GaP-rich quantum barrier insertions were applied to suppress leakage of non-equilibrium electrons from the gain medium. Laser diodes having a threshold current densities of ~7–10 kA/cm2 at room temperature were realized for both (211) and (322) surface orientations at cavity lengths of ~1mm. Emission wavelength at room temperature ~600 nm is shorter by ~8 nm than previously reported. As an opposite example, the devices grown on (811) GaAs substrates did not show lasing at room temperature

Green (In,Ga,Al)P-GaP light-emitting diodes grown on high-index GaAs surfaces

International audienceWe report on green (550–560 nm) electroluminescence (EL) from (Al0.5Ga0.5)0.5In0.5P–(Al0.8Ga0.2)0.5In0.5P double p–i–n heterostructures with monolayer–scale tensile strained GaP insertions in the cladding layers and light–emitting diodes (LEDs) based thereupon. The structures are grown side–by–side on high–index and (100) GaAs substrates by molecular beam epitaxy. Cross–sectional transmission electron microscopy studies indicate that GaP insertions are flat, thus the GaP–barrier substrate orientation–dependent heights should match the predictions of the flat model. At moderate current densities (~500 A/cm2) the EL intensity of the structures is comparable for all substrate orientations. Opposite to the (100)–grown strictures, the EL spectra of (211) and (311)–grown devices are shifted towards shorter wavelengths (~550 nm at room temperature). At high current densities (>1 kA/cm2) a much higher EL intensity is achieved for the devices grown on high–index substrates. The integrated intensity of (311)–grown structures gradually saturates at current densities above 4 kA/cm2, whereas no saturation is revealed for (211)–grown structures up to the current densities above 14 kA/cm2. We attribute the effect to the surface orientation–dependent engineering of the GaP band structure which prevents the escape of the nonequilibrium electrons into the indirect conduction band minima of the p– doped (Al0.8Ga0.2)0.5In0.5P cladding layers

InGaAlP/GaAs Injection Lasers of the Orange Optical Range (~600 nm)

Lasing in the orange spectral range (599–605 nm) is demonstrated for (AlxGa1 –x)0.5In0.5P–GaAs laser diodes grown by metalorganic vapor-phase epitaxy (MOVPE) on GaAs (211)A and (322)A substrates. The active region consists of four layers of InxGa1 –xP vertically coupled quantum dots. The leakage of nonequilibrium electrons from the active region is suppressed by barriers consisting of four quantum-confinement layers of the InGaAlP solid solution with a high Ga content. The maximal optical output power in the pulsed regime is 800 mW and is limited by the catastrophic optical degradation of mirrors. The lasers fabricated from structures grown on (322)A substrates have a lower threshold current density, higher differential quantum efficiency, and smaller internal losses when compared with lasers fabricated from structures grown on (211)A substrates, which is explained by the higher barrier for nonequilibrium electrons in the first case