Pseudomorphic growth and strain relaxation of α-Zn3P2 on GaAs(001) by molecular beam epitaxy

Bosco, Jeffrey P.; Kimball, Gregory M.; Lewis, Nathan S.; Atwater, Harry A.

doi:10.1016/j.jcrysgro.2012.10.054

Cited by 29 publications

(45 citation statements)

References 34 publications

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“…The growth of Zn 3 P 2 from a compound sublimation source has been studied in detail previously. 19 The Zn 3 P 2 compound-source material was synthesized from elemental Zn and P (99.9999%, Alfa Aesar). 20,21 Zn-doped GaAs(001) substrates were used as an epitaxial template.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Under these conditions, stoichiometric Zn 3 P 2 films have been reported to grow epitaxially with excellent crystallinity along the (001) direction. 19 Zinc-blende ZnSe and wurtzite CdS films were also grown by compound-source MBE in the same vacuum chamber. ZnSe films have been reported to grow using congruent sublimation from a compound source with similar crystalline and optoelectronic quality to films grown with separate elemental sources.…”

Section: Experimental Methodsmentioning

confidence: 99%

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Energy-band alignment of II-VI/Zn3P2 heterojunctions from x-ray photoemission spectroscopy

Bosco

Scanlon

Watson

et al. 2013

Journal of Applied Physics

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The energy-band alignments for zb-ZnSe(001)/a-Zn 3 P 2 (001), w-CdS(0001)/a-Zn 3 P 2 (001), and w-ZnO(0001)/a-Zn 3 P 2 (001) heterojunctions have been determined using high-resolution x-ray photoelectron spectroscopy via the Kraut method. Ab initio hybrid density functional theory calculations of the valence-band density of states were used to determine the energy differences between the core level and valence-band maximum for each of the bulk materials. The ZnSe/Zn 3 P 2 heterojunction had a small conduction-band offset, DE C , of À0.03 6 0.11 eV, demonstrating a nearly ideal energy-band alignment for use in thin-film photovoltaic devices. The CdS/Zn 3 P 2 heterojunction was also type-II but had a larger conduction-band offset of DE C ¼ À0.76 6 0.10 eV. A type-III alignment was observed for the ZnO/Zn 3 P 2 heterojunction, with DE C ¼ À1.61 6 0.16 eV indicating the formation of a tunnel junction at the oxide-phosphide interface. The data also provide insight into the role of the II-VI/Zn 3 P 2 band alignment in the reported performance of Zn 3 P 2 heterojunction solar cells. V C 2013 AIP Publishing LLC. [http://dx

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Section: Experimental Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Energy-band alignment of II-VI/Zn3P2 heterojunctions from x-ray photoemission spectroscopy

Bosco

Scanlon

Watson

et al. 2013

Journal of Applied Physics

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“…The Zn 3 P 2 grew in the tetragonal (a-phase) crystal structure along the (001) direction with a 45 in-plane rotation with respect to the GaAs lattice, as reported previously. 24 The Zn 3 P 2 showed a streaky RHEED diffraction pattern, indicating that relatively smooth epitaxial films had been formed. A weak half-order reconstruction was also observed, which can be attributed to a Znterminated surface reconstruction.…”

Section: à3mentioning

confidence: 99%

“…16,24 Standard Knudsen effusion cells were used as compound sublimation sources for both Zn 3 P 2 and ZnS. Epi-ready, Zn-doped (>1 Â 10 18 cm À3 ), p-type GaAs(001) single crystal wafers (AXT) were used as an epitaxial substrate.…”

Section: Dementioning

confidence: 99%

Band alignment of epitaxial ZnS/Zn3P2 heterojunctions

Bosco

Demers

Kimball

et al. 2012

Journal of Applied Physics

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A unique photoemission method to measure semiconductor heterojunction band offsets Appl. Phys. Lett. 102, 012101 (2013) Charge carrier relaxation and effective masses in silicon probed by terahertz spectroscopy J. Appl. Phys. 112, 123704 (2012) Digging up bulk band dispersion buried under a passivation layer Appl. Phys. Lett. 101, 242103 (2012) A combined hard x-ray photoelectron spectroscopy and electrical characterisation study of metal/SiO2/Si(100) metal-oxide-semiconductor structures Appl. Phys. Lett. 101, 241602 (2012) Determination of the deep donor-like interface state density distribution in metal/Al2O3/n-GaN structures from the photocapacitance-light intensity measurement

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“…This is in good agreement with Bosco et al, who report a carrier concentration of ∼1 × 10 17 cm −3 for Zn 3 P 2 epilayers prepared with the same process. 19,22 The current versus bias voltage transport curves across the graphene−Zn 3 P 2 junction, I(V B ), are shown in Figure 3A,B. The measurements are taken in dc mode at room temperature and ambient conditions with the graphene electrode grounded (Au−C), the V B is applied to the Zn 3 P 2 via the Ag electrode and the V G is applied via the Au−G electrode.…”

mentioning

confidence: 99%

Performance Enhancement of a Graphene-Zinc Phosphide Solar Cell Using the Electric Field-Effect

Vazquez‐Mena

Bosco²,

Ergen

et al. 2014

Nano Lett.

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ABSTRACT:The optical transparency and high electron mobility of graphene make it an attractive material for photovoltaics. We present a field-effect solar cell using graphene to form a tunable junction barrier with an Earth-abundant and low cost zinc phosphide (Zn 3 P 2 ) thin-film light absorber. Adding a semitransparent top electrostatic gate allows for tuning of the graphene Fermi level and hence the energy barrier at the graphene-Zn 3 P 2 junction, going from an ohmic contact at negative gate voltages to a rectifying barrier at positive gate voltages. We perform current and capacitance measurements at different gate voltages in order to demonstrate the control of the energy barrier and depletion width in the zinc phosphide. Our photovoltaic measurements show that the efficiency conversion is increased 2-fold when we increase the gate voltage and the junction barrier to maximize the photovoltaic response. At an optimal gate voltage of +2 V, we obtain an open-circuit voltage of V oc = 0.53 V and an efficiency of 1.9% under AM 1.5 1-sun solar illumination. This work demonstrates that the field effect can be used to modulate and optimize the response of photovoltaic devices incorporating graphene. KEYWORDS: Graphene, zinc phosphide, field effect solar cell, Schottky barrier, earth-abundant materials, photovoltaics T he extraordinary properties of graphene, such as its high carrier mobility, Fermi-level tuning and its high optical transparency, make it an attractive candidate to improve the performance of optoelectronic and photovoltaic devices. 1−3 These properties can be exploited for tackling some of the major challenges in solar energy. One challenge is to exploit Earth-abundant and low-cost synthesis materials with band gaps suitable for solar energy conversion. Besides common PV absorbers like Si, CdTe, and CIGS, there are other materials that have the potential for large scale solar implementation at lower costs, such as zinc phosphide (Zn 3 P 2 ), copper zinc tin sulfide (CZTS), cuprous oxide (Cu 2 O), and iron sulfide (FeS 2 ). 4 However, the lack of doping processes necessary to form homojuntions and the absence of complementary emitter materials to form high quality p−n heterojunction have limited the conversion efficiency of devices incorporating these materials. These limitations can be addressed using graphene, which has previously been used to form graphene−semiconductor junctions 5 and solar cells with CdS and CdSe 6,7 semiconductors as well as with Si,5,[8][9][10][11] demonstrating Schottky barrier behavior. 5 Further advances on graphene−semiconductor junctions were demonstrated by building gate-controlled devices in order to modify the Schottky barrier height and the electrical transport across the junction. This design has been used to build a graphene−Si transistor (barristor) 12 and a graphene−organic thin film junction transistors. 9,13 Herein, we study the barrier tuning of a graphene−Zn 3 P 2 field-effect solar cell with a semitransparent top-gate electrode and demonstrate that this tunin...

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Pseudomorphic growth and strain relaxation of α-Zn3P2 on GaAs(001) by molecular beam epitaxy

Cited by 29 publications

References 34 publications

Energy-band alignment of II-VI/Zn3P2 heterojunctions from x-ray photoemission spectroscopy

Energy-band alignment of II-VI/Zn3P2 heterojunctions from x-ray photoemission spectroscopy

Band alignment of epitaxial ZnS/Zn3P2 heterojunctions

Performance Enhancement of a Graphene-Zinc Phosphide Solar Cell Using the Electric Field-Effect

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