Reduction of the ZnSe/GaAs(100) valence band offset by a Te interlayer

Gleim, Th.; Heske, C.; Umbach, E.; Schumacher, C.; Faschinger, W.; Ammon, Ch.; Probst, Matthias; Steinrück, Hans‐Peter

doi:10.1063/1.1358366

Cited by 19 publications

(10 citation statements)

References 19 publications

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“…Layers of ZnSe and its alloys with Cd, Mg, Te or S can be grown epitaxially on III-V single crystalline substrates such as GaAs or InP for device applications. [4][5][6][7] The deposition methods are vapor-phase methods, mainly molecular beam epitaxy [4][5][6] and metal-organic chemical vapor deposition. 7 Epitaxial deposition from aqueous solutions at lower temperatures either chemically or by electrodeposition represents another approach even if the control of the electronic properties is far less advanced than for classical methods.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Deposition of ZnSe from Dimethyl Sulfoxide Solution and Characterization of Epitaxial Growth

et al. 2004

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In this work, we studied the conditions for the electrodeposition of ZnSe films from dimethyl sulfoxide solutions with a special focus on epitaxial growth. We examined the influence of experimental parameters such as the nature of the substrate, temperature, and hydrodynamic conditions. The investigated substrates were glass covered with SnO2:F, molybdenum and (1̄1̄1̄) or (100) n−InP substrates. The voltammetric behavior of the Zn(II)−Se−DMSO system showed that the mechanism of ZnSe film formation is strongly dependent on the nature of the substrate. Films prepared at constant potential were characterized by scanning electron microscopy (SEM), electron dispersive spectroscopy (EDS), atomic force microscopy (AFM), reflection of high energy electron diffraction (RHEED), transmission electron microscopy (TEM) and also by optical measurements. Epitaxial growth of ZnSe was obtained on (100) and (1̄1̄1̄) n−InP crystalline planes with good quality as demonstrated by RHEED patterns and TEM measurements, a result that confirms that electrodeposition provides an alternative route to obtain epitaxial films of ZnSe.

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Section: Introductionmentioning

confidence: 99%

Electrochemical Deposition of ZnSe from Dimethyl Sulfoxide Solution and Characterization of Epitaxial Growth

et al. 2004

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“…The UPS and IPES spectra of the ion-treated CZTSSe, 25 nm In x S y /CZTSSe, and annealed 25 nm In x S y /CZTSSe samples are shown on a common energy axis relative to E F in Figure . The valence band maximum (VBM) and conduction band minimum (CBM) were determined with a linear extrapolation of the leading edge of the respective spectrum. , …”

Section: Resultsmentioning

confidence: 99%

“…The valence band maximum (VBM) and conduction band minimum (CBM) were determined with a linear extrapolation of the leading edge of the respective spectrum. 42,43 For the CZTSSe absorber, we derive the VBM and CBM to 0.60 ± 0.10 and 0.97 ± 0.15 eV, respectively. These positions indicate that the absorber's downward band bending toward the surface is relatively weak.…”

Section: T H Imentioning

confidence: 99%

Intermixing at the In_xS_y/Cu₂ZnSn(S,Se)₄ Heterojunction and Its Impact on the Chemical and Electronic Interface Structure

Hauschild

Mezher

Schnabel

et al. 2019

ACS Appl. Energy Mater.

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We report on the chemical and electronic structure of the interface between a thermally co-evaporated In x S y buffer and a Cu 2 ZnSn(S,Se) 4 (CZTSSe) absorber for thin-film solar cells that, to date, has achieved energy conversion efficiencies up to 8.6 %. Using surface-sensitive x-ray and UV photoelectron spectroscopy, combined with inverse photoemission and bulksensitive soft x-ray emission spectroscopy, we find a complex character of the buffer layer. It includes oxygen, as well as selenium and copper that diffused from the absorber into the In x S y buffer, exhibits an electronic band gap of 2.50 ± 0.18 eV at the surface, and leads to a small cliff in the conduction band alignment at the In x S y /CZTSSe interface. After an efficiencyincreasing annealing step at 180 °C in nitrogen atmosphere, additional selenium diffusion leads to a reduced band gap at the buffer layer surface (2.28 ± 0.18 eV).

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“…The valence band maximum (VBM) was determined by linear extrapolation of the leading edge in the UPS valence band spectra. [39] XES was conducted at Beamline 8.0.1 of the ALS, utilizing the high-transmission variable-line spacing (VLS) spectrometer of the SALSA endstation, [40] calibrated with the S L 2,3 emission spectrum of CdS. [41,42] The base pressure in the UNLV and SALSA analysis chambers was <5×10 -10 and <5×10 -9 mbar, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…The XPS and XAES spectra were calibrated using Auger and core-level peaks of clean Cu, Ag, and Au foils, and UPS spectra were calibrated with the Fermi energy of a sputter-cleaned Au foil. The valence band maximum (VBM) was determined by linear extrapolation of the leading edge in the UPS valence band spectra . XES was conducted at Beamline 8.0.1 of the ALS, utilizing the high-transmission variable-line spacing (VLS) spectrometer of the SALSA endstation, calibrated with the S L 2,3 emission spectrum of CdS. , The base pressure in the UNLV and SALSA analysis chambers was <5 × 10 –10 and <5 × 10 –9 mbar, respectively.…”

Section: Methodsmentioning

confidence: 99%

Variations in the Chemical and Electronic Impact of Post-Deposition Treatments on Cu(In,Ga)(S,Se)₂ Absorbers

Mezher

Mansfield

Horsley

et al. 2019

ACS Appl. Energy Mater.

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Keywords: alkali post-deposition treatment, chalcopyrite thin-film solar cell, photoelectron spectroscopy, x-ray emission spectroscopy, potassium fluoride, sodium fluorideWe present a comparative study that focuses on the variability of postdeposition treatments (NaF-PDT and KF-PDT) and their impact on the chemical and electronic structure of chalcopyrite thin film solar cell absorbers. For this purpose, two "extreme" chalcopyrite absorber systems are studied: Cu(In,Ga)(S,Se) 2 with industrial relevance (STION), and Cu(In,Ga)Se 2 with "research grade" properties (NREL). Samples were subjected to NaF-PDT and KF-PDT, and investigated using x-ray and ultraviolet photoelectron spectroscopy, Auger electron spectroscopy, as well as synchrotron-based soft x-ray emission spectroscopy. Considerably different alkali-induced effects are found for the two systems. In particular, we only detect a PDT-related Cu depletion on the NREL absorber surfaces (and only on those leading to high-efficiency devices). We also observe a reduction in the surface S/Se ratio for all alkali-treated STION absorbers, in addition to the presence of sulfates after the KF-PDT. After processing the PDT absorbers to 2 fully operating cells, we find that the PDT temperature has a significant impact on the resulting device efficiencies -both the NREL and STION absorbers can result in high-efficiency and low-efficiency devices, depending on KF-PDT processing parameters. The absorbers of low-efficiency KF-PDT devices show the largest Cu surface content after PDT, causing the valence band maximum to be closer to the Fermi energy, thus possibly leading to less efficient charge-carrier separation and/or enhanced recombination at the interface. Finally, we find varying degrees of Na, K, and/or F residuals on the different absorber surfaces after PDT, indicating a potential "hidden" parameter in employing PDTs for improved solar cell performance.

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Reduction of the ZnSe/GaAs(100) valence band offset by a Te interlayer

Cited by 19 publications

References 19 publications

Electrochemical Deposition of ZnSe from Dimethyl Sulfoxide Solution and Characterization of Epitaxial Growth

Electrochemical Deposition of ZnSe from Dimethyl Sulfoxide Solution and Characterization of Epitaxial Growth

Intermixing at the In_xS_y/Cu₂ZnSn(S,Se)₄ Heterojunction and Its Impact on the Chemical and Electronic Interface Structure

Variations in the Chemical and Electronic Impact of Post-Deposition Treatments on Cu(In,Ga)(S,Se)₂ Absorbers

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Reduction of the ZnSe/GaAs(100) valence band offset by a Te interlayer

Cited by 19 publications

References 19 publications

Electrochemical Deposition of ZnSe from Dimethyl Sulfoxide Solution and Characterization of Epitaxial Growth

Electrochemical Deposition of ZnSe from Dimethyl Sulfoxide Solution and Characterization of Epitaxial Growth

Intermixing at the InxSy/Cu2ZnSn(S,Se)4 Heterojunction and Its Impact on the Chemical and Electronic Interface Structure

Variations in the Chemical and Electronic Impact of Post-Deposition Treatments on Cu(In,Ga)(S,Se)2 Absorbers

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Intermixing at the In_xS_y/Cu₂ZnSn(S,Se)₄ Heterojunction and Its Impact on the Chemical and Electronic Interface Structure

Variations in the Chemical and Electronic Impact of Post-Deposition Treatments on Cu(In,Ga)(S,Se)₂ Absorbers