Luminescent N-polar (In,Ga)N/GaN quantum wells achieved by plasma-assisted molecular beam epitaxy at temperatures exceeding 700 °C

Chèze, Caroline; Feix, Felix; Lähnemann, Jonas; Flissikowski, Timur; Kryśko, M.; Wolny, P.; Turski, Henryk; Skierbiszewski, C.; Brandt, O.

doi:10.1063/1.5009184

Cited by 15 publications

(5 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Because of the high reactivity of Al with O, the doping level could very well be substantially higher than in GaN (see, e.g., ref 42 for studies of metal-polar films), but we are not aware of data for N-polar (Al,Ga)N. For GaN of either polarity, there is general agreement that O incorporation is reduced substantially with increasing growth temperature. 43,44 Our nanowires were grown at temperatures not accessible for planar layers (820 °C), and we would thus expect that O incorporation is reduced even further. For a quantitative estimate, we examined the APT data for the presence of O but also C, Ca, and B (which are the most abundant impurities in GaN layers grown by PAMBE).…”

Section: Nano Lettersmentioning

confidence: 99%

Absence of Quantum-Confined Stark Effect in GaN Quantum Disks Embedded in (Al,Ga)N Nanowires Grown by Molecular Beam Epitaxy

et al. 2019

Self Cite

View full text Add to dashboard Cite

Several of the key issues of planar (Al,Ga)N-based deep-ultraviolet light emitting diodes could potentially be overcome by utilizing nanowire heterostructures, exhibiting high structural perfection and improved light extraction. Here, we study the spontaneous emission of GaN/(Al,Ga)N nanowire ensembles grown on Si(111) by plasmaassisted molecular beam epitaxy. The nanowires contain single GaN quantum disks embedded in long (Al,Ga)N nanowire segments essential for efficient light extraction. These quantum disks are found to exhibit intense emission at unexpectedly high energies, namely, significantly above the GaN bandgap, and almost independent of the disk thickness. An in-depth investigation of the ac-tual structure and composition of the nanowires reveals a spontaneously formed Al gradient both along and across the nanowire, resulting in a complex core/shell structure with an Al deficient core and an Al rich shell with continuously varying Al content along the entire length of the (Al,Ga)N segment. This compositional change along the nanowire growth axis induces a polarization doping of the shell that results in a degenerate electron gas in the disk, thus screening the built-in electric fields. The high carrier density not only results in the unexpectedly high transition energies, but also in radiative lifetimes depending only weakly on temperature, leading to a comparatively high internal quantum efficiency of the GaN quantum disks up to room temperature. arXiv:1905.04090v1 [cond-mat.mes-hall]

show abstract

Section: Nano Lettersmentioning

confidence: 99%

Absence of Quantum-Confined Stark Effect in GaN Quantum Disks Embedded in (Al,Ga)N Nanowires Grown by Molecular Beam Epitaxy

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…It is likely related to the difference in defect formation mechanics, e.g. higher layer contamination [5,6] for growths in the N-polar orientation by metalorganic vapor phase epitaxy (MOVPE) and by molecular beam epitaxy (MBE) [4,[7][8][9][10], due to the drastically different growth dynamics and chemistry of the N-polar and Ga-polar structures. If the reason for the low IQE of N-polar quantum wells is discovered and solved, and the IQE is brought up to the level of Ga-polar heterostructures, constructing LEDs (or laser diodes) requires placing the quantum wells inside the depletion region of a p-n junction diode.…”

Section: Introductionmentioning

confidence: 99%

Polarization control in nitride quantum well light emitters enabled by bottom tunnel-junctions

Turski

Bharadwaj

Xing

et al. 2019

Journal of Applied Physics

View full text Add to dashboard Cite

The frozen internal polarization-induced electric fields due to broken inversion symmetry in all conventional blue and green nitride semiconductor light emitting semiconductor quantum well heterostructures point in a direction opposite to what is desired for efficient flow of electrons and holes. This state of affairs has persisted because of the desire to have p-type hole injectors on top of the quantum well active region. Because of the internal polarization fields in nitride heterostructures, there exist four permutations of doping and polarization for the realization of such light emitters. Which permutation is the most desirable for efficient light emission? In this work, we answer this question by demonstrating a fundamentally new approach towards efficient light emission with bottom-tunnel junctions. The bottomtunnel junction design aligns the polarization fields in a desired direction in the quantum well, while simultaneously eliminating the need for p-type contacts, and allowing efficient current spreading. By preventing electron overshoot past quantum wells, it disables carrier recombination in undesired regions of the quantized heterostructures, and opens up the possibility for new geometries of integrating and stacking multiple light emitters. Due to the inherent advantages, the bottom-tunnel junction light emitting diode enables a 200-300% increase in the light emission efficiency over alternate heterostructure designs.

show abstract

“…We recall that these layers were grown at about 700 and 715 ℃, respectively. Chèze et al [23] have also reported a slightly larger Ca concentration of 3 -5 × 10 17 cm −3 for a N-polar GaN buffer grown by PA-MBE at 730 ℃ whereas Young et al [24] found only 8×10 15 cm −3 of Ca impurties in a Ga-polar GaN buffer grown by NH 3 -MBE at 820 ℃. Hence, in addition to the growth temperature [24], the Ca incorporation rate appears to be drastically affected by the MBE growth method and the crystal orientation.…”

Section: B Impurity Concentrationmentioning

confidence: 97%

“…The origin of this phenomenon is related to the presence of nonradiative defects at the QW/barrier interface. A potential candidate for this as yet unknown point defect is * Electronic mail: auzelle@pdi-berlin.de the impurity Ca [22,23] which can contaminate the substrate surface during wet cleaning and gradually incorporates in the overgrown nitride layers [24].…”

Section: Introductionmentioning

confidence: 99%

Interface recombination in Ga- and N-polar GaN/(Al,Ga)N quantum wells grown by molecular beam epitaxy

Auzelle,

Sinito,

Lähnemann

et al. 2021

Preprint

View full text Add to dashboard Cite

We explore and systematically compare the morphological, structural and optical properties of GaN/(Al,Ga)N multiple quantum wells (MQWs) grown by plasma-assisted molecular beam epitaxy (PA-MBE) on freestanding GaN(0001) and GaN(000 1) substrates. Samples of different polarity are found to be on par in terms of their morphological and structural perfection and exhibit essentially identical quantum well widths and Al content. Regardless of the crystal orientation, the exciton decay in the MQWs at 10 K is dominantly radiative and the photoluminescence (PL) energy follows the quantum confined Stark effect (QCSE) for different quantum well widths. A prominent free-to-bound transition involving interface shallow donors is, however, visible for the N-polar MQWs. At room-temperature, in contrast, the exciton decay in all samples is dominated by nonradiative recombination taking place at point defects, presumably Ca or V 𝑁 located at the bottom QW interface. Remarkably, the N-polar MQWs exhibit a higher PL intensity and longer decay times than the Gapolar MQWs at room-temperature. This improved internal quantum efficiency is attributed to the beneficial orientation of the internal electric field that effectively reduces the capture rate of minority carriers by interface trap states.

show abstract

Luminescent N-polar (In,Ga)N/GaN quantum wells achieved by plasma-assisted molecular beam epitaxy at temperatures exceeding 700 °C

Cited by 15 publications

References 32 publications

Absence of Quantum-Confined Stark Effect in GaN Quantum Disks Embedded in (Al,Ga)N Nanowires Grown by Molecular Beam Epitaxy

Absence of Quantum-Confined Stark Effect in GaN Quantum Disks Embedded in (Al,Ga)N Nanowires Grown by Molecular Beam Epitaxy

Polarization control in nitride quantum well light emitters enabled by bottom tunnel-junctions

Interface recombination in Ga- and N-polar GaN/(Al,Ga)N quantum wells grown by molecular beam epitaxy

Contact Info

Product

Resources

About