Giant electric fields in unstrained GaN single quantum wells

Langer, Róbert; Simon, Julia; Ortiz, V.; Pelekanos, N. T.; Barski, A.; André, R.; Godlewski, M.

doi:10.1063/1.124193

Cited by 186 publications

(118 citation statements)

References 14 publications

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“…4 The net polarization and consequent internal electric fields have been shown to be detrimental to the performance of optoelectronic devices. [5][6][7][8][9] Polarization discontinuities lead to band bending and result in the quantum confined Stark effect in ͑0001͒ oriented III-nitride quantum well ͑QW͒ structures. The consequences of this effect include decreased recombination efficiency, redshifted emission, and blueshifting of the emission with increasing drive current.…”

Section: Introductionmentioning

confidence: 99%

Strain-induced polarization in wurtzite III-nitride semipolar layers

Романов

Baker

Nakamura

et al. 2006

Journal of Applied Physics

668

487

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This paper presents growth orientation dependence of the piezoelectric polarization of InxGa1−xN and AlyGa1−yN layers lattice matched to GaN. This topic has become relevant with the advent of growing nitride based devices on semipolar planes [A. Chakraborty et al., Jpn. J. Appl. Phys., Part 2 44, L945 (2005)]. The calculations demonstrate that for strained InxGa1−xN and AlyGa1−yN layers lattice matched to GaN, the piezoelectric polarization becomes zero for nonpolar orientations and also at another point ≈45° tilted from the c plane. The zero crossover has only a very small dependence on the In or Al content of the ternary alloy layer. With the addition of spontaneous polarization, the angle at which the total polarization equals zero increases slightly for InxGa1−xN, but the exact value depends on the In content. For AlyGa1−yN mismatched layers the effect of spontaneous polarization becomes important by increasing the crossover point to ∼70° from c-axis oriented films. These calculations were performed using the most recent and convincing values for the piezoelectric and elasticity constants, and applying Vegard’s law to estimate the constants in the ternary InxGa1−xN and AlyGa1−yN layers.

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Section: Introductionmentioning

confidence: 99%

Strain-induced polarization in wurtzite III-nitride semipolar layers

Романов

Baker

Nakamura

et al. 2006

Journal of Applied Physics

668

487

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“…However, these fields cause spatial separation of electrons and holes in quantum wells that are used for active regions in light emitters. Such a separation increases the recombination time 1 at the expense of the quantum efficiency, 2 and also results in a red shift of the emission, the amount of which depends on the injected carrier density due to screening. In short, additional constraints are placed on design rules in an effort to deal with polarization induced field.…”

Section: Introductionmentioning

confidence: 99%

Defect reduction in (112¯) a-plane GaN by two-stage epitaxial lateral overgrowth

Özgür

et al. 2006

Applied Physics Letters

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In the epitaxial lateral overgrowth (ELO) of (1120) a-plane GaN, the uneven growth rates of two opposing wings, Ga-and N-wings, makes the coalescence of two neighboring wings more difficult than that in c-plane GaN. We report a two-stage growth method to get uniformly coalesced epitaxial lateral overgrown a-plane GaN using metalorganic chemical vapor deposition (MOCVD) by employing relatively lower growth temperature in the first step followed by enhanced lateral growth in the second. Using this method, the height differences between Ga-polar and N-polar wings at the coalescence front could be reduced, thereby making the coalescence of two wings much easier. Transmission electron microscopy (TEM) showed that the threading dislocation density in the wing areas was 1.0×10 8 cm -2 , more than two orders of magnitude lower than that in the window areas (4.2×10 10 cm -2 ). However, high density of basal stacking faults of 1.2×10 4 cm -1 was still observed in the wing areas as compared to c-plane GaN. Atomic force microscopy and photoluminescence

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“…This built-in electric field originates from the in-plane strain-induced piezoeffect due to the lattice mismatch between the QW and barrier materials and the spontaneous polarization of the wurtzite structure, and its strength can be as high as several MV/ cm. [4][5][6][7] The main experimentally observed signature of optically induced screening is a blueshift in QW photoluminescence ͑PL͒ with an increase in excitation density, as it indicates the flattening of the band structure due to decrease of the bias field. This blueshift was observed, for example, in InGaN / GaN samples in intense cw excitation regime 8 and in AlGaN / GaN samples in intense nanosecond pulse excitation regime.…”

Section: Introductionmentioning

confidence: 99%

Role of dynamical screening in excitation kinetics of biased quantum wells: Nonlinear absorption and ultrabroadband terahertz emission

Turchinovich

Monozon

Jepsen

2006

Journal of Applied Physics

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In this work we describe the ultrafast excitation kinetics of a biased quantum well, arising from the optically induced dynamical screening of a bias electric field. The initial bias electric field inside the quantum well is screened by the optically excited polarized electron-hole pairs. This leads to a dynamical modification of the properties of the system within an excitation pulse duration. We calculate the excitation kinetics of a biased quantum well and the dependency of resulting electronic and optical properties on the excitation pulse fluence, quantum well width, and initial bias field strength. Our calculations, in particular, predict the strongly nonlinear dependency of the effective optical absorption coefficient on the excitation pulse fluence, and ultrabroadband terahertz emission. Our theoretical model is free of fitting parameters. Calculations performed for internally biased InGaN / GaN quantum wells are in good agreement with our experimental observations ͓Turchinovich et al., Phys. Rev. B 68, 241307͑R͒ ͑2003͔͒, as well as in perfect compliance with qualitative considerations.

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Giant electric fields in unstrained GaN single quantum wells

Cited by 186 publications

References 14 publications

Strain-induced polarization in wurtzite III-nitride semipolar layers

Strain-induced polarization in wurtzite III-nitride semipolar layers

Defect reduction in (112¯) a-plane GaN by two-stage epitaxial lateral overgrowth

Role of dynamical screening in excitation kinetics of biased quantum wells: Nonlinear absorption and ultrabroadband terahertz emission

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