Characterization of ZnSiP₂ Films Grown on Si Substrate by Liquid Phase Epitaxy: Morphology, Composition, and Interface Microstructure

Abstract

The exploration and growth of novel cost-effective top cell materials is one of the great hot topics for the development of Si-based tandem solar cells. ZnSiP2 was thought to be a promising candidate of the top cell material for the Si tandem solar cell. In this work, ZnSiP2 single crystal film with the stoichiometric ratio was successfully grown on a Si substrate by the liquid phase epitaxy method for the first time. The surface morphology, thickness, composition, and the orientation of the film were characterized by SEM, EDS, EPMA, and the high-resolution XRD. The results show that a continuous epitaxial ZnSiP2 film with the thickness of 3 μm was grown on the Si substrate. In addition to this continuous film, many island single crystals were also observed on the surface of the film. The high-resolution XRD φ scan results indicated that the film as well as these isolated islands crystallized with the same orientation, c-orientation with respect to the (100) Si substrate, without any misoriented domains. The microstructure of the ZnSiP2/Si interface characterized by the high-resolution transmission electron microscopy image, as well as the selected area electron diffraction patterns of the ZnSiP2 thin films and Si substrates, also confirmed the epitaxial growth of ZnSiP2 on the Si substrate. The electrical conductivity σ, Hall mobility μH, and carrier concentrations n of the ZnSiP2 film were 1.38 × 10–5 Ω–1 cm–1, 94.5 cm–2 V–1 s–1, and 9.11 × 109 cm–3, respectively. Our work paves the way for the development of ZnSiP2 silicon-based tandem solar cell devices.

Utilizing Site Disorder in the Development of New Energy-Relevant Semiconductors

“…A 2018 paper, by Martinez et al, investigated the growth of amorphous and epitaxial ZnSiP 2 −Si alloys on Si using a carbon-free chemical vapor deposition process. 99 Liquid-phase epitaxy was utilized to grow stoichiometric and epitaxial ZnSiP 2 films on Si in a 2019 paper, by Zhang et al 100 Despite these promising bulk crystal and epitaxial thin-film results, low current remains as the main limiting factor in ZnSiP 2 device efficiency. One avenue to solve this limitation is to induce enough cation disorder to shrink the band gap.…”

“…Improving this device fabrication step is one important component in reducing the overall vast and growing energy consumption of data centers . Materials including ZnGeP 2 and ZnSiP 2 , which are lattice-matched to Si, may be grown directly on Si for active components. − Cation disorder may be used to enable order/disorder heterostructure devices, but a remaining challenge is to increase the optical absorption–emission strength, as the ordered materials have direct but symmetry-forbidden optical transitions …”

Recent advances in designing thermoelectric materials

“…Several experimental studies also verified this approach with improved ZT values. [325][326][327][328] Crystal symmetry is largely determined by atomic ordering in a system. Therefore, altering atomic arrangements also can influence the transport properties.…”

Epitaxial ZnGeP2 Thin Films on Si and GaP by Reactive Combinatorial Sputtering in Phosphine

“…The existing literature on thin film synthesis of ZnGeP 2 is limited, with a few recent reports of polycrystalline thin films ,, and only two papers from the late 1980s and early 90s on epitaxial growth. , In the work conducted by Xing, et al, epitaxial ZnGeP 2 on GaP and Si substrates were synthesized via metalorganic vapor-phase epitaxy (MOVPE). They observed changes in the lattice constant and cation ordering in the ZnGeP 2 films as a function of the film composition. , Similar chalcopyrite and zinc blende II–IV–V 2 materials, such as ZnSiP 2 , ZnSnP 2 , ZnSnAs 2 , CdSnP 2 , and MgGeAs 2 , have been synthesized by means of molecular beam epitaxy (MBE), − liquid-phase epitaxy (LPE), , low-pressure chemical vapor deposition with a combination of hydride and elemental precursors, and vapor–liquid–solid growth . The use of sputtering for the synthesis of epitaxial II–IV–P 2 materials has not yet been explored but has been utilized to grow polycrystalline ZnGeP 2 films .…”

“…They observed changes in the lattice constant and cation ordering in the ZnGeP 2 films as a function of the film composition. 13,14 Similar chalcopyrite and zinc blende II−IV− V 2 materials, such as ZnSiP 2 , ZnSnP 2 , ZnSnAs 2 , CdSnP 2 , and MgGeAs 2 , have been synthesized by means of molecular beam epitaxy (MBE), 15−17 liquid-phase epitaxy (LPE), 18,19 lowpressure chemical vapor deposition with a combination of hydride and elemental precursors, 20 and vapor−liquid−solid growth. 21 The use of sputtering for the synthesis of epitaxial II−IV−P 2 materials has not yet been explored but has been utilized to grow polycrystalline ZnGeP 2 films.…”