Effects of stacking on the structural and optical properties of self-organized GaN/AlN quantum dots

Gogneau, N.; Fossard, F.; Monroy, E.; Monnoye, Sylvain; Mank, Hugues; Daudin, B.

doi:10.1063/1.1755840

Cited by 35 publications

(35 citation statements)

References 15 publications

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“…It is worth to notice that for all these dots, the aspect ratio, i.e. L d /D, is in the range of 0.15 to 0.21, typical for vertically correlated GaN/AlN QDs [3,4]. One can see that for QDs with larger D, U(L br ) and E c-v (L br ) depend stronger on L br .…”

Section: Band-to-band Transition Energy [Ev]mentioning

confidence: 95%

Quantum confined Stark effect in vertically correlated GaN/AlN quantum dots

Łepkowski

Jurczak

2006

Phys. Status Solidi (c)

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We investigate Quantum Confined Stark Effect (QCSE) in vertically correlated wurtzite GaN/AlN QDs, having hexagonal pyramid-shape. We show that the QCSE in these structures depends not only on the vertical dimensions, i.e., the height of the QDs and the thickness of the barriers, but also on their base diameter. We show that for typical wurtzite GaN/AlN QDs, having the base diameter of 19.5nm, drop of the electrostatic potential in the QD region slightly increases with increasing the width of barriers. Consequently, the band-to-band transition energies in the QDs decrease. Qualitatively similar but a factor of two stronger dependences is obtained for superlattices of QWs having the same vertical dimensions. The increase of the base diameter of the dots results in stronger dependences of both the electrostatic potential and the band-to-band transition energy on the thickness on barriers.1 Introduction Optical properties of nitride heterostructures are dominated by the presence of high built-in electric field which reduces the emission energy and separates electron and hole wavefunctions decreasing the transition probability. This represent the well-known Quantum Confined Stark Effect (QCSE). For the case of nitride quantum wells (QWs), the QCSE was studied by many groups [1,2]. Particularly in was shown that for periodic multi-quantum well systems, the absolute value of the built-in electric field and thus the magnitude of QCSE depends on both, the thickness of QWs and barriers [2].We extend the analysis of the QCSE to nitride quantum dots. Particularly, we focus on vertically correlated wurtzite GaN/AlN QDs which have been recently grown by several groups [3][4][5]. Vertically correlated GaN/AlN QDs are considered as new candidates for the active region in blue or UV light emitters [6]. One expects that the three dimensional carrier confinement present in nitride QDs can increase the optical material gain and decrease the non-radiative recombination in comparison with conventionally used nitride quantum wells. Moreover, it occurs that strong built-in electric fields present in nitride QDs, due to spontaneous and piezoelectric polarizations, make these structures attractive for quantum information processing or spintronics [7]. This is mainly due to strong and intrinsic excitonexciton coupling possible in these structures. For these reasons, accurate analysis of the QCSE in these structures is crucial for proper design.In this paper, we investigate the QCSE of wurtzite GaN/AlN QDs, having hexagonal pyramid-shape, stacked in the multilayer. We show how electrostatic potential and energy of band-to-band transition depend on the height of the QDs, L d , the base diameter of the QDs, D, and the width of AlN barrier, L br .

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Section: Band-to-band Transition Energy [Ev]mentioning

confidence: 95%

Quantum confined Stark effect in vertically correlated GaN/AlN quantum dots

Łepkowski

Jurczak

2006

Phys. Status Solidi (c)

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“…The sample studied was grown by plasma assisted molecular beam epitaxy on 6H-SiC(0001) using the modified Stranski-Krastanow growth mode after the deposition of 6 monolayers of GaN [6]. It consists of a stack of 200 periods of GaN QDs separated by 8 nm wide AlN barriers.…”

Section: Experimental 21 Sample Descriptionmentioning

confidence: 99%

“…Different processes may change the strain from layer to layer in a stack of QDs. First, the vertical transmission of the strain field will change the deformation of the QDs and the barrier as the superlattice builds up, influencing the QD morphology and optical properties [5,6]. Second, samples with different AlN or GaN coverage will display a different strain balance [4].…”

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confidence: 99%

Depth profiling of optical and vibrational properties in GaN/AlN quantum dot superlattices

Cros

Fresneda

Budagosky

et al. 2009

Physica Status Solidi (b)

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Spatially resolved confocal μ‐Raman and μ‐photoluminescence experiments were performed to analyze the vibrational and optical properties of GaN/AlN quantum dots as a function of depth. Two approaches have been followed. First, spectra were taken by defocusing the microscope objective at various depths on the sample surface. In a second set of experiments a bevel at an angle of 20° with respect to the surface normal was prepared by mechanical polishing of the surface, and spectra were taken across the bevel. The E2h vibrational modes ascribed to the GaN QDs and the AlN spacer redshift towards the surface, indicating the progressive relaxation of the QDs and a considerable increase of the tensile strain in the AlN spacer. The photoluminescence is found to blueshift and narrow towards the surface. This behaviour is ascribed to the decrease of the QD internal electric field as a consequence of the relaxation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…It was observed that overgrowth of GaN QWs with AlN at high temperatures results in an irregular thinning of the QW thickness owing to exchange of Ga-atoms in the GaN layer with Al [5]. This is a thermally activated phenomenon that becomes relevant for AlN growth temperatures above 730 • C.…”

Section: Si-doped Gan/aln Multiple-quantum-well Structuresmentioning

confidence: 99%

MBE growth of nitride-based photovoltaic intersubband detectors

Monroy

Guillot

Leconte

et al. 2006

Superlattices and Microstructures

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In this work, we present the plasma-assisted molecular-beam epitaxial growth of quantum well infrared photodetector (QWIP) structures, including the Si-doped GaN/AlN short-period superlattice of the active region, conductive AlGaN claddings and integration of the final device. The growth of Si-doped GaN/AlN multiple quantum well (QW) structures is optimized by controlling substrate temperature, metal excess and growth interruptions. Structural characterization confirms a reduction of the interface roughness to the monolayer scale. P-polarized intersubband absorption peaks covering the 1.33-1.91 µm wavelength range are measured on samples with QW thickness varying from 1 to 2.5 nm. The absorption exhibits Lorentzian shape with a line width around 100 meV in QWs doped 5 × 10 19 cm −3 . To prevent partial depletion of the QWs owing to the internal electric field, we have developed highly-conductive Si-doped AlGaN cladding layers using In as a surfactant during growth. Complete ISB photodetectors with 40 periods of 1 nm-thick Si-doped GaN QWs with 2 nm-thick AlN barriers have been grown on conductive AlGaN claddings, the Al mole fraction of the cladding matching the average Al content of the active region. Temperature-dependent photovoltage measurements reveal a narrow (∼90 meV) detection peak at 1.39 µm.

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Effects of stacking on the structural and optical properties of self-organized GaN/AlN quantum dots

Cited by 35 publications

References 15 publications

Quantum confined Stark effect in vertically correlated GaN/AlN quantum dots

Quantum confined Stark effect in vertically correlated GaN/AlN quantum dots

Depth profiling of optical and vibrational properties in GaN/AlN quantum dot superlattices

MBE growth of nitride-based photovoltaic intersubband detectors

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