Quantification of Bi distribution in MOVPE-grown Ga(AsBi) via HAADF STEM

Knaub, Nikolai; Beyer, Andreas; Wegele, T.; Ludewig, Peter; Volz, Kerstin

doi:10.1016/j.jcrysgro.2015.10.007

Cited by 11 publications

(6 citation statements)

References 34 publications

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“…Careful inspection of the experimental Bi profiles across individual QWs (see figure 3) reveal that the profile resembles segregation curves, with its characteristic profile and exponential-like decaying tail. Note that recent experimental investigations of the microstructure of GaAsBi/GaAs MQWs grown using single-growth-temperature methods demonstrate that Bi segregation is significantly strong in this material system, even for MQWs grown at the low substrate temperature of 220 °C [23,27,28]. We find that the experimental Bi profiles of MQWs grown using the TST method are still well described using Muraki's phenomenological segregation model [29].…”

Section: Transmission Electron Microscopysupporting

confidence: 47%

GaAsBi/GaAs multi-quantum well LED grown by molecular beam epitaxy using a two-substrate-temperature technique

et al. 2017

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We report a GaAsBi/GaAs multiple quantum well (MQW) light emitting diode (LED) grown by molecular beam epitaxy using a two-substrate-temperature (TST) technique. In particular, the QWs and the barriers in the intrinsic region were grown at the different temperatures of [Formula: see text] = 350 °C and [Formula: see text] respectively. Investigations of the microstructure using transmission electron microscopy (TEM) reveal homogeneous MQWs free of extended defects. Furthermore, the local determination of the Bi distribution profile across the MQWs region using TEM techniques confirm the uniform Bi distribution, while revealing a slightly chemically graded GaAs-on-GaAsBi interface due to Bi surface segregation. Despite this small broadening, we found that Bi segregation is significantly reduced (up to 18% reduction) compared to previous reports on Bi segregation in GaAsBi/GaAs MQWs. Hence, the TST procedure proves as a very efficient method to reduce Bi segregation and thus increase the quality of the layers and interfaces. These improvements positively reflect in the optical properties. Room temperature photoluminescence and electroluminescence (EL) at 1.23 μm emission wavelength are successfully demonstrated using TST MQWs containing less Bi content than in previous reports. Finally, LED fabricated using the present TST technique show current-voltage (I-V) curves with a forward voltage of 3.3 V at an injection current of 130 mA under 1.0 kA cm current excitation. These results not only demonstrate that TST technique provides optical device quality GaAsBi/GaAs MQWs but highlight the relevance of TST-based growth techniques on the fabrication of future heterostructure devices based on dilute bismides.

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Section: Transmission Electron Microscopysupporting

confidence: 47%

GaAsBi/GaAs multi-quantum well LED grown by molecular beam epitaxy using a two-substrate-temperature technique

et al. 2017

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“…The majority of these studies have explored phase stability and compositional homogeneity in MBE-grown films using rapid thermal anneals (RTA) in the temperature and time ranges of 500 °C-800 °C and tens of seconds, respectively [13][14][15][16][17][18][19]. Several have employed photoluminescence (PL) spectroscopy to track changes in the opto-electronic properties, x-ray diffraction to assess film composition and stability of superlattice structures, and methods of transmission electron microscopy (TEM) to explore phase stability, Bi clustering and Bi segregation [13][14][15][17][18][19][20][21][22][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Annealing-induced precipitate formation behavior in MOVPE-grown GaAs_1−xBi_xexplored by atom probe tomography and HAADF-STEM

et al. 2017

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The effects of a 45 min anneal at 800 °C on the physical properties and microstructure of a five-period GaAs Bi /GaAs Bi superlattice with y ≠ x were studied using room-temperature photoluminesence spectroscopy, high-resolution x-ray diffraction, high-angle annular-dark-field scanning transmission electron microscopy (HAADF-STEM), and atom probe tomography (APT). The anneal resulted in a substantial increase of the photoluminesence intensity over that observed in the as-deposited sample, indicating annihilation of non-radiative recombination centers and stability of the superlattice structure during the anneal. However, some precipitation of Bi from the GaAs Bi also occurred. The characteristics of phase separation that occurred within these precipitates were investigated in detail by APT and HAADF-STEM. They indicate that the precipitation reaction involves formation of embedded nano-scale liquid droplets that can accelerate local Bi dissolution from the GaAs Bi matrix by moving through it. Preservation of nanometer scale sharp Bi concentration gradients in the growth direction suggested that very little solid state diffusion of Bi occurred during the anneal. The observed gradient in precipitate number density with distance from the sample surface further supports hypotheses of an enabling role of Ga vacancies in the precipitation process.

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“…Nevertheless, the impact of thermodynamics cannot be omitted and theoretical predictions are supported by recent experimental studies demonstrating that under specific circumstances cluster formation, phase separation and atomic ordering do occur in III-V-Bi [4][5][6][7][8], which can significantly affect their optical and electrical properties. While most of these phenomena concern epilayers (thickness >40 nm), the microstructure of quantum wells (QWs), which are otherwise the proposed structure for many optoelectronic applications, is presently under active investigation [9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Spontaneous formation of three-dimensionally ordered Bi-rich nanostructures within GaAs_1−xBi_x/GaAs quantum wells

Luna

Hanke

et al. 2016

Nanotechnology

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In this work, we report on the spontaneous formation of ordered arrays of nanometer-sized Bi-rich structures due to lateral composition modulations in Ga(As,Bi)/GaAs quantum wells grown by molecular beam epitaxy. The overall microstructure and chemical distribution is investigated using transmission electron microscopy. The information is complemented by synchrotron x-ray grazing incidence diffraction, which provides insight into the in-plane arrangement. Due to the vertical inheritance of the lateral modulation, the Bi-rich nanostructures eventually shape into a three-dimensional assembly. Whereas the Bi-rich nanostructures are created via two-dimensional phase separation at the growing surface, our results suggest that the process is assisted by Bi segregation which is demonstrated to be strong and more complex than expected, implying both lateral and vertical (surface segregation) mass transport. As demonstrated here, the inherent thermodynamic miscibility gap of Ga(As,Bi) alloys can be exploited to create highly uniform Bi-rich units embedded in a quantum confinement structure.

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Quantification of Bi distribution in MOVPE-grown Ga(AsBi) via HAADF STEM

Cited by 11 publications

References 34 publications

GaAsBi/GaAs multi-quantum well LED grown by molecular beam epitaxy using a two-substrate-temperature technique

GaAsBi/GaAs multi-quantum well LED grown by molecular beam epitaxy using a two-substrate-temperature technique

Annealing-induced precipitate formation behavior in MOVPE-grown GaAs_1−xBi_xexplored by atom probe tomography and HAADF-STEM

Spontaneous formation of three-dimensionally ordered Bi-rich nanostructures within GaAs_1−xBi_x/GaAs quantum wells

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Quantification of Bi distribution in MOVPE-grown Ga(AsBi) via HAADF STEM

Cited by 11 publications

References 34 publications

GaAsBi/GaAs multi-quantum well LED grown by molecular beam epitaxy using a two-substrate-temperature technique

GaAsBi/GaAs multi-quantum well LED grown by molecular beam epitaxy using a two-substrate-temperature technique

Annealing-induced precipitate formation behavior in MOVPE-grown GaAs1−xBixexplored by atom probe tomography and HAADF-STEM

Spontaneous formation of three-dimensionally ordered Bi-rich nanostructures within GaAs1−xBix/GaAs quantum wells

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Product

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Annealing-induced precipitate formation behavior in MOVPE-grown GaAs_1−xBi_xexplored by atom probe tomography and HAADF-STEM

Spontaneous formation of three-dimensionally ordered Bi-rich nanostructures within GaAs_1−xBi_x/GaAs quantum wells