A Stress‐Free and Textured GaP Template on Silicon for Solar Water Splitting

Abstract

This work shows that a large-scale textured GaP template monolithically integrated on Si can be developed by using surface energy engineering, for watersplitting applications. The stability of (114)A facets is first shown, based on scanning tunneling microscopy images, transmission electron microscopy, and atomic force microscopy. These observations are then discussed in terms of thermodynamics through density functional theory calculations. A stressfree nanopatterned surface is obtained by molecular beam epitaxy, composed of a regular array of GaP (114)A facets over a 2 in. vicinal Si substrate. The advantages of such textured (114)A GaP/Si template in terms of surface gain, band lineups, and ohmic contacts for water-splitting applications are finally discussed.photosemiconductor catalysts [4,5] is definitely the most promising tech nology for the near future with potentially plethora of hydrogen provided in a clean and sustainable manner. Many recent proposals deal with the use of the GaP semiconductor as a photoelectrode in PEC devices, [6] especially because its bandgap (2.26 eV) is larger than the 1.73 eV photo potential needed for water splitting. [7] Using this idea, demonstrations of GaP based PEC devices [8][9][10][11] and descriptions of the physics/chemistry of the standard GaP surface, [12] its interaction with water [13,14] and hydrogen generation [15] were reported. To enhance conversion efficiency of GaP based PEC devices, strategies like surface functionalization, [10] use of plasmon resonant nanostructures, [16] or integration of nanowires [17] were considered. Meanwhile, it was demonstrated recently that the texturation of surfaces at the electrode level greatly enhances the efficiency of BiVO 4 photoanodes in PEC devices. [18] Structuration of semiconductor surfaces can be per formed by lithography techniques, [19] chemical processes, [20,21] nanowires, or by a selforganization during the epitaxial process of the material itself. [22] This last approach is usually driven by crystal strainrelief processes; it simplifies the postgrowth device processing but does not offer large degrees of freedom,

A Novel Charge Transfer Channel to Simultaneously Enhance Photocatalytic Water Splitting Activity and Stability of CdS

“…Solar energy conversion is a promising approach for solving solar water splitting using semiconductor photocatalysts as an attractive development to produce hydrogen from renewable and clean water resources, which has attracted widespread attention . Among numerous semiconductor materials, such as ZnO, CdS, BiVO 4 , g‐C 3 N 4 , Ta 3 N 5 , SrTiO 3 , Co 9 S 8 , GaP, Ga 2 O 3 , NiSe and CoO, CdS has been widely explored as a visible light responsive photocatalytic material due to its intrinsic advantages, including proper band‐edge positions, narrow bandgap, and high efficiency for photocatalytic hydrogen production . However, more reported application of CdS is severely limited owing to suffering from poor carrier separation, severe surface recombination, and photocorrosion.…”

Epitaxial III–V/Si Vertical Heterostructures with Hybrid 2D‐Semimetal/Semiconductor Ambipolar and Photoactive Properties

“…The surface appears rough, with visible inclusions of anti‐phase materials in the main phase matrix. To further identify and study the local properties of the singularities, independently of the roughness and faceting induced by emerging APBs, [ 19 ] an APB developing treatment (combining chemical mechanical polishing (CMP) and etching processes, [ 20 ] as described in the Supporting Information) was used. A typical SEM image of the same sample after APB developing treatment is given in the inset of Figure 1b, showing the nice improvement of the surface smoothness in individual single‐phase domains (below 3 nm root‐mean‐square roughness), and the clear identification of emerging APBs distribution (see also Figure S2, Supporting Information, for a SEM image at a larger scale).…”

Photoelectrochemical water oxidation of GaP1−xSbx with a direct band gap of 1.65 eV for full spectrum solar energy harvesting

“…This results in an average unintentional n-doping level of 10 18 cm À3 , acting as electrical shunts in the structure. 18,19 Photogenerated carriers in the GaP 0.67 Sb 0.33 epilayer are then brought to the surface or to the GaP 0.67 Sb 0.33 /Si interface more easily. Finally, the presence of APBs is also expected to create intermediate bandgap energy levels.…”

“…The band diagram of GaP 0.67 Sb 0.33 is calculated using an extended basis sp 3 d 5 s* tight binding Hamiltonian. 18,39 This method has proved to provide a band structure description with a sub-millielectronvolt precision throughout the Brillouin zone of binary cubic III-V and II-VI 27 semiconductors including quantum heterostructures 40 and surfaces. 41 From the tight binding parameters of GaP and GaSb binary compounds, 42 a virtual crystal approximation is performed to obtain the GaP 0.67 Sb 0.33 alloy band structure.…”