| 1. |
- Huang, Dan, et al.
(författare)
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Ideal half-filled intermediate band position in CuGaS 2 generated by Sb-related defect complex: A first-principles study
- 2019
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Ingår i: Applied Physics Express. - : IOP Publishing. - 1882-0786 .- 1882-0778. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- Cu-based chalcopyrite compounds have attracted much attention for photovoltaic application, while some of them (like CuGaS 2 ) have energy gaps greater than the optimal value. An isolated and half-filled intermediate band located at the lower part of its original band gap exhibits in CuGaS 2 with (Sb Ga + Zn Ga ) or (Sb Ga + V Cu ) defect complex, in line with the intrinsic p-type conductivity of the host, revealed from our first-principles calculations. Subsequently, the absorption coefficients of CuGaS 2 can cover the full solar light spectrum efficiently. Based on the defect formation energy calculations, however, these defect complexes are hard to reach a large concentration under equilibrium condition. Nevertheless, non-equilibrium growth methods are suggested to prepare samples inheriting the excellent adsorption coefficients.
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| 2. |
- Okujima, Masahiro, et al.
(författare)
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Molecular beam epitaxial growth of GaAs/GaNAsBi core-multishell nanowires
- 2021
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Ingår i: APPLIED PHYSICS EXPRESS. - : IOP Publishing Ltd. - 1882-0778 .- 1882-0786. ; 14:11
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Tidskriftsartikel (refereegranskat)abstract
- GaAs/GaNAsBi/GaAs core-multishell nanowires were grown using molecular beam epitaxy on Si(111) substrates. The formation of the 20 nm wide GaNAsBi shell with a regular hexagonal structure was observed. The shell is estimated to contain approximately 1.5% N and 2.6% Bi and has a compressive lattice mismatch of less than 0.2% with GaAs layers. The strain mediation by the introduction of both N and Bi suppresses the crystalline deformation, resulting in the clear formation of the GaNAsBi shell. Thus, we obtained room-temperature photoluminescence with the maximum position at approximately 1300 nm from the GaAs/GaNAsBi/GaAs core-multishell nanowires.
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| 3. |
- Tsutsumi, Rikuo, et al.
(författare)
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Outermost AlGaO(x)native oxide as a protection layer for GaAs/AlGaAs core-multishell nanowires
- 2020
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Ingår i: APPLIED PHYSICS EXPRESS. - : IOP PUBLISHING LTD. - 1882-0778 .- 1882-0786. ; 13:7
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Tidskriftsartikel (refereegranskat)abstract
- We propose native oxide AlGaO(x)outer protective layer for GaAs/AlGaAs core-multishell nanowires to provide yearly stable stronger optical and electrical confinement within the nanowire core. We prepared core-multishell NWs consisting of GaAs core, Al0.2Ga0.8As multi-layered barrier layer, and amorphous Al(0.9)Ga(0.1)O(x)outer shell, which was obtained simply by growing Al-rich AlGaAs and exposing the NWs to the ambient air. Photoluminescence from the NWs reveals that the Al(0.9)Ga(0.1)O(x)outer shell provides efficient optical confinement and creates a compressive strain in the interior of the NW that enhances and blueshifts the photoluminescence of the GaAs core.
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| 4. |
- Yapparov, Rinat, et al.
(författare)
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Optimization of barrier height in InGaN quantum wells for rapid interwell carrier transport and low nonradiative recombination
- 2020
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Ingår i: Applied Physics Expres. - : IOP Publishing. - 1882-0778 .- 1882-0786. ; 13:12
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Tidskriftsartikel (refereegranskat)abstract
- Rapid interwell carrier transport is a key process for a uniform carrier distribution and reduced Auger recombination in multiple quantum well (MQW) light emitting devices. In this work, the interwell transport has been studied by time-resolved photoluminescence in In0.12Ga0.88N MQWs with InxGa1-xN (x = 0 0.06) and Al0.065Ga0.935N barriers. Only for the InGaN barriers the transport is efficient. However, introduction of In into the barriers is accompanied by an increase of the nonradiative recombination at QW interfaces. Still, even with the increased Shockley-Read-Hall recombination, structures with InGaN barriers might be advantageous for high power devices because of the reduced Auger recombination.
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| 5. |
- Fülöp, Attila, 1988, et al.
(författare)
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Phase transition of bismuth telluride thin films grown by MBE
- 2014
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Ingår i: Applied Physics Express. - 1882-0786 .- 1882-0778. ; 7:4, s. Art. no. 045503-
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Tidskriftsartikel (refereegranskat)abstract
- A previously unreported phase transition between Bi2Te3 and Bi4Te3 in bismuth telluride grown by molecular beam epitaxy is recorded via XRD, AFM, and SIMS observations. This transition is found to be related to the Te/Bi beam equivalent pressure (BEP) ratio. BEP ratios below 17 favor the formation of Bi4Te3 while Bi2Te3 is formed at higher ratios. Transport measurements reveal that Bi2Te3 has higher electron mobility than Bi4Te3.
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| 6. |
- Hashemi, Seyed Ehsan, 1986, et al.
(författare)
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Effect of compositional interlayers on the vertical electrical conductivity of Si-doped AlN/GaN distributed Bragg reflectors grown on SiC''
- 2017
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Ingår i: Applied Physics Express. - 1882-0786 .- 1882-0778. ; 10:5, s. 055501-
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the effect of strain-compensating interlayers on the vertical electrical conductivity of Si-doped AlN/GaN distributed Bragg reflectors (DBRs). Samples with 10.5 mirror pairs were grown through plasma-assisted molecular beam epitaxy on SiC. Room-temperature current–voltage characteristics were measured vertically in mesas through 8 of the 10.5 pairs. The sample with no interlayers yields a mean specific series resistance of 0.044 Ω cm2 at low current densities, while three samples with 5/5-Å-thick, 2/2-nm-thick, and graded interlayers have resistivities between 0.16 and 0.34 Ω cm2. Thus, interlayers impair vertical current transport, and they must be designed carefully when developing conductive DBRs.
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| 7. |
- Wang, P., et al.
(författare)
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Heteroepitaxy growth of GaAsBi on Ge(100) substrate by gas source molecular beam epitaxy
- 2016
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Ingår i: Applied Physics Express. - : IOP Publishing. - 1882-0786 .- 1882-0778. ; 9:4
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the growth of GaAsBi single-crystal film on Ge substrate by gas source molecular beam epitaxy. A high-quality GaAsBi epilayer has been obtained. It has been found that the surfactant effect of Bi suppresses the interdiffusion of Ge at the GaAsBi/Ge interface and reduces the misfit dislocation density. The Bi atoms occupy the As sites, as indicated by the appearance of GaBi-like TO(G) and LO(G) phonon modes in Raman spectra. In addition, the redshift of the GaAs-like LO(G) phonon frequency has been observed in the Raman spectra, owing to the Bi-induced biaxial strain and the alloying effect as well.
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| 8. |
- Yue, L., et al.
(författare)
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Novel InGaPBi single crystal grown by molecular beam epitaxy
- 2015
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Ingår i: Applied Physics Express. - : IOP Publishing. - 1882-0786 .- 1882-0778. ; 8:4, s. Art. no. 041201-
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Tidskriftsartikel (refereegranskat)abstract
- InGaPBi crystalline thin films with up to 2.1% bismuth concentration have been grown on GaAs substrates by molecular beam epitaxy. Rutherford backscattering spectrometry confirms that the majority of Bi atoms are located at substitutional lattice sites. The films exhibit good surface, structural, and interface quality, and their strains can be tuned from tensile to compressive by increasing the Bi content. InBi LO and GaBi LO vibrational modes in Raman spectroscopy were observed, and their intensities increased with Bi concentration. A weak photoluminescence signal was observed at 1.78 eV at room temperature for the sample with a Bi content of 0.5%.
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| 9. |
- Fujii, Hitoshi, et al.
(författare)
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Interstitial Donor Codoping Method in (Ga, Mn)As to Increase Solubility of Mn and Curie Temperature
- 2011
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Ingår i: APPL PHYS EXPRESS. - : The Japan Society of Applied Physics (JSAP). - 1882-0778. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- Based on first principles calculations, we propose a solubility control method of magnetic impurities in dilute magnetic semiconductors (DMSs). The low solubility of Mn in (Ga, Mn)As is experimentally and theoretically known. We show that donor atoms, such as Li, introduced at the interstitial sites in GaAs enhance the solubility of Mn. As a result, Mn can be doped to more than 20% in GaAs in the thermal equilibrium condition. The same effect can be seen when we dope Mn in GaAs with other interstitial donors, such as H, Na, K, Be, Mg, Ca, Cu, and Ag.
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| 10. |
- Hayton, James, et al.
(författare)
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Pi-Conjugated Molecular Nanowire Stacks Investigated by Frequency-Modulation Atomic Force Microscopy in the qPlus Configuration
- 2009
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Ingår i: APPLIED PHYSICS EXPRESS. - 1882-0778. ; 2:9, s. 091501-
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembled pi-conjugated nanowire stacks were imaged using a tuning-fork probe mounted in the qPlus configuration in frequency modulation mode under ultrahigh vacuum. High resolution topographic and dissipation images demonstrate the applicability of such probes to soft conjugated materials, with sub-molecular resolution achieved perpendicular to the stacking axis. A new insight is gained from the damping contrast into the local mechanical properties of edge-on pi-conjugated stacks.
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