| 1. |
- Chen, X, et al.
(author)
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Shallow-terrace-like interface in dilute-bismuth GaSb/AlGaSb single quantum wells evidenced by photoluminescence
- 2013
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 113:15, s. 153505-153507
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Journal article (peer-reviewed)abstract
- Photoluminescence (PL) measurements are performed on one GaSb/AlGaSb single-quantum-well (SQW) sample and two dilute-bismuth (Bi) GaSb/AlGaSb SQW samples grown at 360 and 380 °C, at low temperatures and under magnetic fields. Bimodal PL features are identified in the dilute-Bi samples, and to be accompanied by abnormal PL blueshift in the sample grown at 360 °C. The bimodal PL features are found to be from similar origins of band-to-band transition by magneto-PL evolution. Analysis indicates that the phenomenon can be well interpreted by the joint effect of interfacial large-lateral-scale islands and Al/Ga interdiffusion due to Bi incorporation. The interdiffusion introduces about 1-monolayer shrinkage to the effective quantum-well thickness, which is similar to the interfacial islands height, and the both together result in an unusual shallow-terrace-like interface between GaSbBi and AlGaSb. A phenomenological model is established, the Bi content of isoelectronic incorporation and the exciton reduced effective mass are estimated for the GaSbBi sample grown at 380 °C, and a value of about 21 meV/% is suggested for the bandgap bowing rate of GaSbBi. An effective routine is suggested for determining the Bi content and the depth of the shallow-terraces at interface in dilute-Bi SQW structures.
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| 3. |
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| 4. |
- Gu, Yi, et al.
(author)
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Optical properties of InGaAsBi/GaAs strained quantum wells studied by temperature-dependent photoluminescence
- 2013
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In: Chinese Physics B. - : IOP Publishing. - 1674-1056. ; 22:3, s. 037802-
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Journal article (peer-reviewed)abstract
- The effect of bismuth on the optical properties of InGaAsBi/GaAs quantum well structures is investigated using the temperature-dependent photoluminescence from 12 K to 450 K. The incorporation of bismuth in the InGaAsBi quantum well is confirmed and found to result in a red shift of photoluminescence wavelength of 27.3 meV at 300 K. The photoluminescence intensity is significantly enhanced by about 50 times at 12 K with respect to that of the InGaAs quantum well due to the surfactant effect of bismuth. The temperature-dependent integrated photoluminescence intensities of the two samples reveal different behaviors related to various non-radiative recombination processes. The incorporation of bismuth also induces alloy non-uniformity in the quantum well, leading to an increased photoluminescence linewidth.
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| 6. |
- Segercrantz, Natalie, et al.
(author)
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Defect studies in MBE grown GaSbBi layers
- 2013
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In: The 17th European Molecular Beam Epitaxy Workshop (EuroMBE), March 10th-13th, 2013, Levi, Finland.
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Conference paper (peer-reviewed)abstract
- Gallium antimonide is an interesting material both from a material and a device point of view. Thedirect, narrow band gap and high electron mobility makes the compound semiconductor a suitablecandidate for high speed electronics and optoelectric devices. It can also be used as a substratematerial for other ternary or quaternary III–V compounds whose band gaps cover a wide spectralrange from 0.8 to 4.3 ?m. [1]Incorporating Bi into GaSb has shown to have several advantages compared to, for example, GaNSb.Not only is the band gap reduced [2], but the width of the gap depends very weakly on temperature [3]and the electron mobility is higher than that of GaNSb [4]. The spin-orbit splitting is also larger thanthe actual band gap which could be used for suppressing Auger-recombinations [5].Using positron annihilation spectroscopy (PAS) in Doppler broadening mode, we have studiedsamples of GaSbBi epitaxial layers on GaSb substrates. The PAS technique is based on the interactionbetween positrons and electrons in solids and can be used for e.g. vacancy defect characterization inthin layers. The studied samples were MBE-grown and the main varied growth parameter wastemperature, which lead to different Bi concentrations. The Bi concentrations were 0 - 0.7 %, theepitaxial layer thickness was 200 nm. The substrate was Te-doped (n-type) GaSb.From the measured results, differences between the samples grown under different conditions can beclearly observed. A short diffusion length for the positrons is observed in all of the epitaxial layers,which indicates an increase in positron trapping defects in the layers, compared to the substrate.Furthermore, the Doppler broadening annihilation parameters in the epitaxial layers also seem todepend on the growth temperature and hence, also on the Bi concentration. In order to be able todistinguish the influence of the Bi concentration from the influence of vacancy defects on the Dopplerbroadening parameters, more accurate measurements need to be conducted. We hope to achieve abetter understanding of the positron trapping defect in the epitaxial layers by using coincidenceDoppler broadening.
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| 7. |
- Song, Yuxin, 1981, et al.
(author)
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Dilute Bismides for Mid-IR Applications
- 2013
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In: Springer Series in Materials Science. - New York, NY : Springer New York. - 2196-2812 .- 0933-033X. - 9781461481218 ; , s. 1-27
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Book chapter (other academic/artistic)abstract
- Dilute bismides are a group of emerging materials with unique properties. Incorporation of a small amount of Bi in common III–V host materials results in large band-gap reduction and strong spin-orbit splitting, leading to potential applications in mid-infrared (Mid-IR) optoelectronics. In this chapter, we review recent progresses on epitaxy and characterizations of novel bismides, i.e., GaSb1−x Bi x , InSb1 − x Bi x , InAs1 − x Bi x , and InAsSbBi. Although these dilute bismides have been successfully grown, to obtain high Bi incorporations and retain high crystal quality is still very challenging.
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| 8. |
- Song, Yuxin, 1981, et al.
(author)
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Dilute bismides for near and mid-infrared applications
- 2013
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In: 2013 15th International Conference on Transparent Optical Networks (ICTON). - 2162-7339. - 9781479906826 ; , s. 6602735-
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Conference paper (peer-reviewed)abstract
- Dilute bismides are a group of emerging materials with unique properties. Incorporation of a small amount of Bi in common III-V host materials results in large band-gap reduction and strong spin-orbit splitting, leading to potential applications in near-infrared (NIR) and mid-infrared (MIR) optoelectronics. Recent progresses on molecular beam epitaxy (MBE) of novel III-Sb-Bi, i.e. GaSbBi and InSbBi thin films from our group are summarised in this paper. Quantum well structures based on GaSbBi and InGaAsBi aiming for the optical communication window were grown and characterized.
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| 10. |
- Song, Yuxin, 1981, et al.
(author)
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MBE growth of Bi2Te3 for Thermoelectrics
- 2013
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In: Asia Communications and Photonics Conference, ACP. - Washington, D.C. : OSA. - 2162-108X.
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Conference paper (peer-reviewed)abstract
- Molecular beam epitaxy of Bi2Te3 on various substrates for thermoelectric applications is investigated. Growth conditions were optimized based on Si(111) substrates with two different growth techniques, co-deposition followed by crystallization and direct growth. Growth of Bi 2Te3 on GaAs, GaN, et. al. substrates with different crystal directions and offcut angles were investigated. High quality Bi2Te3 thin films were achieved with very low carrier density and record high carrier mobility.
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