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Im, Jin Seo; Kollmer, H.; Off, J.; Sohmer, A.; Scholz, F.; Hangleiter, A.

doi:10.1103/physrevb.57.r9435

Cited by 613 publications

(78 citation statements)

References 13 publications

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“…[1][2][3] However, both device types suffer from a distinct efficiency reduction towards the green spectral range, despite the better confinement properties of energetically deeper QWs. Established reasons for this matter include a reduced electron-hole-overlap in the QWs due to the quantumconfined Stark effect (QCSE) [4][5][6][7][8] and general difficulties in growing homogeneous InGaN material. [9][10][11][12][13][14][15] Also high pumping conditions are known to cause a further reduction of the efficiency that is attributed to Auger recombination.…”

Section: Introductionmentioning

confidence: 99%

Polarization-induced confinement of continuous hole-states in highly pumped, industrial-grade, green InGaN quantum wells

Nippert

Nirschl

Schulz

et al. 2016

Journal of Applied Physics

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We investigate industrial-grade InGaN/GaN quantum wells (QWs) emitting in the green spectral region under high, resonant pumping conditions. Consequently, an ubiquitous high energy luminescence is observed that we assign to a polarization field Confined Hole Continuum (CHC). Our finding is supported by a unique combination of experimental techniques, including transmission electron microscopy, (time-resolved) photoluminescence under various excitation conditions, and electroluminescence, which confirm an extended out-of-plane localization of the CHC-states. The larger width of this localization volume surpasses the QW thickness, yielding enhanced nonradiative losses due to point defects and interfaces, whereas the energetic proximity to the bulk valence band states promotes carrier leakage. Published by AIP Publishing.

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Section: Introductionmentioning

confidence: 99%

Polarization-induced confinement of continuous hole-states in highly pumped, industrial-grade, green InGaN quantum wells

Nippert

Nirschl

Schulz

et al. 2016

Journal of Applied Physics

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“…In the 20 A well MQW sample, the excitonic transition peak position at 10 K is blueshifted with respect to the epilayer by an amount of 63 meV, which is due to the well-known effects of quantum confinement of electrons and holes as well as the strain. Its transition energy (3.548 eV) is comparable to the bandgap of GaN under 0.4% compressive strain, which is expected for GaN embedded between Alo.15Gao.g5N layers [6]. In the 30 A and 40 A well MQW samples, the transition peak positions at 10 K are redshifted with respect to the GaN epilayer by an amount of 17 meV and 57 meV, respectively.…”

mentioning

confidence: 62%

“…Recent work on the Ill-nitride alloy systems and MQWs has shown that localized exciton transitions dominate the optical properties in these systems at low temperatures [2][3][4]. And, it has been proposed that piezoelectric fields due to lattice mismatch-induced strain in InGaN/GaN MQWs [5] and GaN/AlGaN QWs [6] A and 40 A, the excitonic transition peak positions at 10 K are in fact blueshifted with respect to the GaN epilayer at early delay times due to the quantum confinement of photoexcited carriers. Its peak positions shift toward lower energies as delay time increases and become redshifted with respect to the GaN epilayer at long delay times.…”

mentioning

confidence: 99%

“…Using c M =377 GPa, ci 2 =160 GPa, c 13 =114 GPa, c 33 =209 GPa [12], and s r =9.5 [6], we obtain d3i=-1.4xl0" 10 cm/V. Our value of d 3 i is almost the average value between a value of -0.9xl0" 10 cm/V obtained by Im et al [6] and -1.7x10"'° cm/V by Martin et al [13]. This value is also comparable with d33=2.0xl0" 10 cm/V as recently measured by Muensit et al using a laser interferometer [14].…”

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confidence: 99%

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Piezoelectric effects on the optical properties of GaN/AlxGa1−xN multiple quantum wells

Kim

Lin

Jiang

et al. 1998

Applied Physics Letters

105

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Abstract:Piezoelectric effects on the optical properties of GaN/AlGaN multiple quantum wells (MQWs) have been investigated by picosecond time-resolved photoluminescence (PL) measurements. For MQWs with well thickness 30 A and 40 A, the excitonic transition peak positions at 10 K in continuous wave (cw) spectra are redshifted with respect to the GaN epilayer by 17 meV and 57 meV, respectively. The time-resolved PL spectra of the 30 A and 40 A well MQWs reveal that the excitonic transition is in fact blueshifted at early delay times due to quantum confinement of carriers. The spectral peak position shifts toward lower energies as the delay time increases and becomes redshifted at longer delay times. We have demonstrated that the results described above is due to the presence of the piezoelectric field in the GaN wells of GaN/AlGaN MQWs subject to elastic strain together with screening of the photoexcited carriers. By comparing experimental and calculation results, we conclude that the piezoelectric field strength in GaN/Alo.isGao.8sN MQWs has a lower limit value of about 560 kV/cm. The electron and hole wave function distributions have also been obtained. The implication of our findings on the practical applications of GaN based optoelectronic devices is also discussed.

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“…6, the value of τ 1/e is shown to increase with increasing magnitude of the mean field across the QWs. The change in τ 1/e reflects qualitatively the change in the total electric fields across the QWs predicted by the calculated band profiles, and faster radiative recombination rates are attributed to weaker total electric fields across the QWs in a sample due to the reduced spatial separation of the electron and hole wavefunctions [20].…”

Section: Resultsmentioning

confidence: 99%

Room temperature PL efficiency of InGaN/GaN quantum well structures with prelayers as a function of number of quantum wells

Christian

Hammersley

Davies

et al. 2016

Phys. Status Solidi C

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We report on the effects of varying the number of quantum wells (QWs) in an InGaN/GaN multiple QW (MQW) structure containing a 23 nm thick In0.05Ga0.95N prelayer doped with Si. The calculated conduction and valence bands for the structures show an increasing total electric field across the QWs with increasing number of QWs. This is due to the reduced strength of the surface polarisation field, which opposes the built‐in field across the QWs, as its range is increased over thicker samples. Low temperature photoluminescence (PL) measurements show a red shifted QW emission peak energy, which is attributed to the enhanced quantum confined Stark effect with increasing total field strength across the QWs. Low temperature PL time decay measurements and room temperature internal quantum efficiency (IQE) measurements show decreasing radiative recombination rates and decreasing IQE, respectively, with increasing number of QWs. These are attributed to the increased spatial separation of the electron and hole wavefunctions, consistent with the calculated band profiles. It is also shown that, for samples with fewer QWs, the reduction of the total field across the QWs makes the radiative recombination rate sufficiently fast that it is competitive with the efficiency losses associated with the thermal escape of carriers. (© 2016 The Authors. Phys. Status Solidi C published by WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Reduction of oscillator strength due to piezoelectric fields inGaN/Alx

Cited by 613 publications

References 13 publications

Polarization-induced confinement of continuous hole-states in highly pumped, industrial-grade, green InGaN quantum wells

Polarization-induced confinement of continuous hole-states in highly pumped, industrial-grade, green InGaN quantum wells

Piezoelectric effects on the optical properties of GaN/AlxGa1−xN multiple quantum wells

Room temperature PL efficiency of InGaN/GaN quantum well structures with prelayers as a function of number of quantum wells

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