QzqiTime-resolved photolttminescence spectroscopy has been used to investigate carrier decay dynamics~t ifl> in a InXGa, -XASI.-,,NV (x-O.03, y -0.01) epilayer grown on GaAs by metal organic chemical vapor deposition. Time-resolved photohrmineseence (PL) measurements, performed for various 4%L excitation intensities and sample temperatures, indicate that the broad PL emission at low -gm temperature is dominated by localized exciton recombination. Lifetimes in the range of 0.07-0.34 a ns are measured; these photo luminescence iifetimes are significantly shorter than corresponding values obtained for GaAs. In particular, we observe an emission energy dependence of ,the decay lifetime at 10 K, whereby the Iifetime decreases with increasing emission energy across the PL spectrum. This behavior is characteristic of a distribution of localized states, which arises from alloy fluctuations. @ 2000 American institute of l&ecentIy, the quatemary InGaAsN alloy system has attracted a great deal of attention due to its potential application in devices such as next generation multifunction solar cells and optoelectronic devices for optical I-7 The alloy is of fundamental and technocommunications. logical interest because it exhibits an extremely large band gap bowing coefficient (b --14eV) between the HI-N and HI-As bhanes.x The extremely large bowing coefficient permits the InXGal _XAsl _YNYquaternary alloy to maintain lattice match to GaAs, with a wide range of tunable band gap energies smaller than the GSAS band gap for x-3y. Studies of InGaAsN solar cell structures with 1 eV band gap have shown that the quatemary suffers from a short minority carrier diffusion length.z3 More recent work has found that significantly improved minority hole diffusion-lengths may be obtained by thermally annealing the InGaAsN after growth, although minority electron diffusion lengths remain short.' In this letter, we report the results of time-resolved PL spectroscopy studies of an InGaAsN epilayer. Tfds letter is one of the first investigations of the carrier dynamics witfdn InGaAsN.A 3-pm-thick, htGaAsN epilayer was grown at a growth temperature of 590 "C by metal organic chemicaI vapor deposition on a semi-insulating GSAS substrate and terminated with a 5 nm GaAs calp.Trimethylindium, trimethylgallium, arsine, and dimethy:lhydrazine were used as source gases. The nominal In and N molar fractions were 0.03 and 0.01, respectively. The Irr/N incorporation ratio of three has been shown to provide lattice match to GaAs!'9 As grown, the unintentionally doped lhtGaAsN film was p type. After growth, the sample was annealed at 600 "C for 30 min in a nitrogen ambient in order to improve the electrical and optic al properties of the material. 1 Photohtminescence (PL) measurements for various sample temperatures and excitation intensities were performed with the sample mounted on a cold -a)Et&~~i~rnaikjiimg@physksmed" finger and cooled by a closed-cycle helium refrigerator. The sample was optically pumped with 580 nm laser pulses of 10 ps width and ...

The optical properties of AlxGa1−xN alloys with x varied from 0 to 0.35 have been investigated by picosecond time-resolved photoluminescence (PL) spectroscopy. Our results revealed that while the PL intensity decreases with an increase of Al content, the low-temperature PL decay lifetime increases with Al content. These results can be understood in terms of the effects of tail states in the density of states due to alloy fluctuation in the AlxGa1−xN alloys. The Al-content dependence of the energy-tail-state distribution parameter E0, which is an important parameter for determining optical and electrical properties of the AlGaN alloys, has been obtained experimentally. The PL decay lifetime increases with the localization energy and, consequently, increases with Al content. The implications of our findings to III-nitride optoelectronic device applications are also discussed.

Optical resonance modes have been observed in optically pumped microdisk cavities fabricated from 50 Å/50 Å GaN/Al x Ga 1Ϫx N(xϳ0.07) and 45 Å/45 Å In x Ga 1Ϫx N/GaN(xϳ0.15) multiple quantum well structures. Microdisks, approximately 9 m in diameter and regularly spaced every 50 m, were formed by an ion beam etch process. Individual disks were pumped at 300 and 10 K with 290 nm laser pulses focused to a spot size much smaller than the disk diameter. Optical modes corresponding to ͑i͒ the radial mode type with a spacing of 49-51 meV ͑both TE and TM͒ and ͑ii͒ the Whispering Gallery mode with a spacing of 15-16 meV were observed in the GaN microdisk cavities. The spacings of these modes are consistent with those expected for modes within a resonant cavity of cylindrical symmetry, refractive index, and dimensions of the microdisks under investigation. The GaN-based microdisk cavity is compared with its GaAs counterpart and implications regarding future GaN-based microdisk lasers are discussed.

High electron mobility through the edge states in random networks of c-axis oriented wedge-shaped GaN nanowalls grown by molecular beam epitaxy Appl. Phys. Lett. 101, 132109 (2012) InGaP-based InGaAs quantum dot solar cells with GaAs spacer layer fabricated using solid-source molecular beam epitaxy Appl. Phys. Lett. 101, 133110 (2012) Comparative study of surface recombination in hexagonal GaN and ZnO surfaces J. Appl. Phys. 112, 063509 (2012) Self-assembly of InAs ring complexes on InP substrates by droplet epitaxy J. Appl. Phys. 112, 063510 (2012) Reduced thermal quenching in indium-rich self-organized InGaN/GaN quantum dots

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