Excitonic recombination dynamics in non-polar GaN/AlGaN quantum wells

Rosales, Daniel; Gil, Bernard; Bretagnon, Thierry; Guizal, Brahim; Zhang, F.; Okur, Serdal; Monavarian, Morteza; Izyumskaya, N.; Avrutin, Vitaliy; Özgür, Ü.; Morkoç̌, H.; Leach, J. H.

doi:10.1063/1.4865959

Cited by 24 publications

(9 citation statements)

References 39 publications

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“…31 The value of A measured for the (I 1 , X) state is much larger than for excitons in nonpolar (Al,Ga)N/GaN QWs, for which A amounts to only a few ps K −1 . 43,50 This result confirms that crystal-phase quantum structures exhibit improved interfaces and reduced densities of localization centers as compared to planar heterostructures. Quantitatively, we can estimate an upper limit for the oscillator strength f osc < 1.5 × 10 12 cm −2 for N D → 0 [Eq.…”

Section: B Density Of States and Oscillator Strength Of The Stacking-...supporting

confidence: 67%

Stacking faults as quantum wells in nanowires: Density of states, oscillator strength, and radiative efficiency

et al. 2014

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We investigate the nature of excitons bound to I 1 basal-plane stacking faults [(I 1 , X)] in GaN nanowire ensembles by continuous-wave and time-resolved photoluminescence spectroscopy. Based on the linear increase of the radiative lifetime of these excitons with temperature, they are demonstrated to exhibit a two-dimensional density of states, i. e., a basal-plane stacking fault acts as a quantum well. From the slope of the linear increase, we determine the oscillator strength of the (I 1 , X) and show that the value obtained reflects the presence of large internal electrostatic fields across the stacking fault. While the recombination of donor-bound and free excitons in the GaN nanowire ensemble is dominated by nonradiative phenonema already at 10 K, we observe that the (I 1 , X) recombines purely radiatively up to 60 K. This finding provides important insight into the nonradiative recombination processes in GaN nanowires. First, the radiative lifetime of about 6 ns measured at 60 K sets an upper limit for the surface recombination velocity of 450 cm s −1 considering the nanowires mean diameter of 105 nm. Second, the density of nonradiative centers responsible for the fast decay of donor-bound and free excitons cannot be higher than 2 × 10 16 cm −3 . As a consequence, the nonradiative decay of donor-bound excitons in these GaN nanowire ensembles has to occur indirectly via the free exciton state.

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Section: B Density Of States and Oscillator Strength Of The Stacking-...supporting

confidence: 67%

Stacking faults as quantum wells in nanowires: Density of states, oscillator strength, and radiative efficiency

et al. 2014

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“…A best fit of α = 1.15 meV/K, β = 1050 K, E g (0 K) = 3.84 eV ± 1.2 meV, and σ = 18 meV was obtained for the as-grown sample by excluding the data below 100 K and α = 0.89 meV/K, β = 1000 K, E g (0 K) = 3.83 eV ± 0.7 meV, and σ = 10.5 meV for the nanopillars by excluding the data below 50 K. The two samples show an “S-shape” for the peak energy (red-shift, blue-shift, and then red-shift) and a weak “W-shape” for the line width (increase, decrease, and then increase) with rising temperature. Similar phenomena were reported in refs and − . For 5 K < T < 50 K, the 10 meV red-shift and moderately wider line width can be interpreted as weakly localized carriers being thermally activated by the increasing temperature, having a greater opportunity to migrate to deeper localized states.…”

Section: Resultssupporting

confidence: 86%

“…To understand the exciton localization effects of the QW structure grown on SLs, the temperature dependence from 5 to 300 K of the PL spectra was measured with an excitation power of 100 μW. In general, the temperature-dependent behavior is attributed to the potential inhomogeneity and localized character of the carrier recombination . The increasing temperature will induce a band gap shrinkage which is described by the Varshni equation , where E g (0 K) is the transition energy of GaN QW at 0 K, α and β are the Varshni coefficients, σ indicates the degree of the localization effect, and k B is the Boltzmann constant.…”

Section: Resultsmentioning

confidence: 99%

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Near-Strain-Free GaN/AlGaN Narrow Line Width UV Light Emission with Very Stable Wavelength on Excitation Power by Using Superlattices

Chen²,

Kocher

et al. 2020

ACS Appl. Electron. Mater.

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Because of the strong strain in nitrides, superlattice layers have been used to release the strain in the QW and reduce the quantum confined Stark effect. However, few reports discuss comprehensively the strain relaxation behavior and optical performance of a GaN/AlGaN single quantum well (QW) with inserted GaN/AlGaN superlattices (SLs). In this work, we examined a group of graded Al content GaN/ Al x Ga 1−x N SL layers under the GaN/Al 0.3 Ga 0.7 N single QW grown on c-plane sapphire. Both the excitation power and temperature dependence of the time-integrated microphotoluminescence (μ-PL) and time-resolved μ-PL were measured. The samples exhibited very narrow UV emission and had almost unchanged emission wavelength and stable line width behavior with excitation power as well as "S-shape" and weak "Wshape" characteristics with temperature due to the localization. The temperaturedependent PL lifetime was measured from 5 to 300 K, and the relatively fast recombination lifetime of the two samples was examined. Micro-Raman spectroscopy was also conducted to probe the strain state. All the results showed that adopting SLs around the QW structure produced a much more stable and desirable performance, which can be attributed to an effective relaxation of the strain in the QW.

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“…Conventional c‐ plane III‐nitrides are characterized by spontaneous and piezoelectric polarization due to the lack of inversion symmetry in the wurtzite crystal structure . Interface charges from polarization discontinuities result in distortions in the energy landscape that induce the quantum‐confined Stark effect (QCSE), increase the carrier recombination lifetime, reduce the optical gain, and negatively affect charge transport and carrier injection . Alteration of these important material properties also significantly impacts optoelectronic and electronic device performance.…”

Section: Introductionmentioning

confidence: 99%

A Decade of Nonpolar and Semipolar III-Nitrides: A Review of Successes and Challenges

Monavarian

Rashidi

Feezell

2018

Phys. Status Solidi A

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The performance of III-nitride devices is degraded by polarization in a wurtzite crystal structure. Nonpolar and semipolar III-nitrides have been extensively studied since the early 2000s as a solution to the polarizationrelated issues. Removal of polarization is expected to improve the radiative efficiency, optical gain, charge transport, and potentially offer solutions to the challenging problems in III-nitride light-emitting diodes (LEDs) known as efficiency droop and the green gap. In addition, use of nonpolar and semipolar orientations is also predicted to offer polarization pinning in some devices due to anisotropic in-plane strain. Despite the many potential advantages over c-plane, nonpolar and semipolar optoelectronic devices have not successfully replaced conventional c-plane devices in the commercial sector. Here, nonpolar and semipolar III-nitrides are reviewed after more than a decade of development. The successes and challenges of nonpolar and semipolar orientations for applications such as LEDs, laser diodes, superluminescent diodes, and vertical-cavity surface emitting lasers are discussed. New potential avenues for nonpolar and semipolar III-nitrides are also highlighted, including visible-light communication and power electronics. The availability of low-cost, high-crystal-quality substrates with nonpolar or semipolar orientation is discussed and alternative approaches for realizing these orientations are presented, including selective-area bottom-up nanostructures.

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Excitonic recombination dynamics in non-polar GaN/AlGaN quantum wells

Cited by 24 publications

References 39 publications

Stacking faults as quantum wells in nanowires: Density of states, oscillator strength, and radiative efficiency

Stacking faults as quantum wells in nanowires: Density of states, oscillator strength, and radiative efficiency

Near-Strain-Free GaN/AlGaN Narrow Line Width UV Light Emission with Very Stable Wavelength on Excitation Power by Using Superlattices

A Decade of Nonpolar and Semipolar III-Nitrides: A Review of Successes and Challenges

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