Time-resolved photoluminescence studies of InGaN/GaN multiple quantum wells

Allègre, J.; Lefèbvre, Pierre; Juillaguet, Sandrine; Knap, W.; Camassel, Jean; Chen, Q.; Khan, M. Asif

doi:10.1557/s1092578300001605

Cited by 10 publications

(4 citation statements)

References 17 publications

(20 reference statements)

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“…2, also varies continuously, but in a nearly exponential way, over more than four orders of magnitude. Figure 2 also displays equivalent data extracted from the literature [5,11,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] for a variety of samples embedding InGaN/GaN QWs, and for our other QW and QB samples. There is a general trend: an InGaN/GaN system emitting UV light will show a decay time of a few nanoseconds, whereas another one emitting red light will rather decay on a time scale of tens of microseconds.…”

Section: Methodsmentioning

confidence: 99%

Carrier Dynamics in Group-III Nitride Low-Dimensional Systems: Localization versus Quantum-Confined Stark Effect

Lefèbvre

Taliercio

Kalliakos

et al. 2001

phys. stat. sol. (b)

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Continuous-wave and time-resolved optical spectroscopy is used to examine a variety of InGaN/GaN quantum-well and quantum-box samples, grown by molecular beam epitaxy. The results are analyzed in order to clarify the respective influences of electric fields and of carrier localizations on radiative recombinations. The coupling of electron-hole pairs with LO-phonons is also studied in detail, from careful analysis of the size-dependent intensities of LO-phonon replica. From our attempt of modelling the Huang-Rhys factor, S, for excitons in these systems, we conclude that the observed optical recombinations are rather those of electrons and holes separately localized on different potential fluctuations.Introduction All efficient light-emitting devices based on group-III nitride semiconductors involve low-dimensional systems, such as InGaN/GaN [1][2][3] or GaN/AlGaN [4] quantum wells (QWs). An intense research activity has been devoted recently to radiative recombinations in these artificial materials. For InGaN-based nanometric layers, large Stokes shifts have been readily assigned to strong carrier localization, possibly in self-formed quantum dots [5,6]. This idea was supported by observations of In-rich nanoclusters in InGaN layers. Although this clustering may depend on the growth conditions, the random distribution of In atoms induces rather strong potential fluctuations, in the volume of this ternary alloy. These fluctuations, together with large carrier effective masses in group-III nitrides, induce the localization of electron and hole wave-functions on nanometric scales, which prevents their efficient capture by nonradiative centers, related to the high density of threading dislocations. This localization was invoked to interpret (i) the strong Stokes shift between photoluminescence (PL) lines and the absorption onset of InGaN epilayers and QWs and (ii) the rather long PL decay times observed in these systems. Now, for all QWs based on nitrides in their wurtzite phase, including InGaN/GaN ones, electric fields of several hundred kV/cm are present, if the growth axis is (0001). Indeed, this symmetry permits spontaneous and piezoelectric polarizations which are specially strong for group-III nitrides [7,8]. These fields reduce drastically the oscillator strength for the ground-state optical transition, as evidenced [9, 10] by very large, sizedependent, recombination times. They are also partly at the origin of the Stokes shift observed in QWs [11].

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Section: Methodsmentioning

confidence: 99%

Carrier Dynamics in Group-III Nitride Low-Dimensional Systems: Localization versus Quantum-Confined Stark Effect

Lefèbvre

Taliercio

Kalliakos

et al. 2001

phys. stat. sol. (b)

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“…First, we will illustrate the electric field effects on PL decay times for InGaN/GaN QWs, multiple QWs and QBs. Figure 7 presents a collection of results gathered from the literature [40,58,[65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80] and from our experiments, aimed at demonstrating any correlation between the PL decay time and the PL energy. This correlation exists, but there is some scattering in the data, with variations of τ P L as large as two orders of magnitude for a given transition energy.…”

Section: Delay (Ns)mentioning

confidence: 99%

Optical properties of group-III nitride quantum wells and quantum boxes

Taliercio

Lefèbvre²,

Gallart

et al. 2001

J. Phys.: Condens. Matter

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We propose an overview of specific optical properties of quantum-size artificial structures made of group-III nitride semiconductors with natural wurtzite symmetry. We consider the cases of quantum wells and of quantum boxes obtained by the Stranski-Krastanov growth mode. We comment on results of continuous-wave and time-resolved optical spectroscopy, in comparison with our envelope-function calculations of excitonic energies and oscillator strengths. The influence on recombination dynamics of internal electric fields and carrier localization is discussed in detail.

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“…Two aspects are of particular importance, namely the photon energy hν of the emitted light and the recombination lifetime τ . During the past few years, therefore, many groups have studied the luminescence behaviour of a wide range of InGaN/GaN single and multi-QW structures in an effort to pin down the precise recombination mechanisms at work and to relate them to the physical characteristics of these structures [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Nevertheless, there is still considerable controversy concerning the detailed interpretation of the experimental results.…”

Section: Introductionmentioning

confidence: 99%

Photoluminescence studies of InGaN/GaN multi-quantum wells

Davidson

Dawson

Wang

et al. 2000

Semicond. Sci. Technol.

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We report measurements of photoluminescence, photoluminescence excitation spectroscopy and photoluminescence time decay on three MOVPE-grown InGaN/GaN multiple quantum well structures with 13% In in the wells and well widths L z = 1.25, 2.5 and 5.0 nm. The PL spectra are dominated by single emission peaks, together with phonon sidebands spaced by a GaN LO phonon energy (92 meV). The peak energies are red-shifted with respect to energies calculated for exciton recombination in square quantum wells and the wide well sample also shows a significant Stokes shift between emission and absorption. Recombination lifetimes measured at 6 K are energy dependent, increasing as the photon energy is scanned downwards through the emission line. They also depend strongly on well width. On the low energy side of the 5 nm well emission line we measure lifetimes as long as 100 ns. Raising the temperature from 6 to 300 K results in a strong reduction of emission intensity for all samples and reduction of the lifetimes, though by a much smaller factor. The peak positions shift slightly to lower energy but by far less than the shift in the band edge. We consider three different theoretical models in an attempt to interpret this data, an exponential tail state model, a model of localization due to In/Ga segregation within the wells and the quantum confined Stark effect model. The QCSE model appears able to explain most of the data reasonably well, though there is evidence to suggest that, in addition, some degree of localization occurs.

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Time-resolved photoluminescence studies of InGaN/GaN multiple quantum wells

Cited by 10 publications

References 17 publications

Carrier Dynamics in Group-III Nitride Low-Dimensional Systems: Localization versus Quantum-Confined Stark Effect

Carrier Dynamics in Group-III Nitride Low-Dimensional Systems: Localization versus Quantum-Confined Stark Effect

Optical properties of group-III nitride quantum wells and quantum boxes

Photoluminescence studies of InGaN/GaN multi-quantum wells

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