Surface Photovoltage Study of GaAsSbN and GaAsSb Layers Grown by LPE for Solar Cells Applications

The properties of GaAsSbN and GaAsSb layers grown by liquid-phase epitaxy on n-GaAs substrates were investigated in a comparative plan with a view of their possible application in multi-junction solar cells. To avoid non-uniformity effects in the composition of these compounds with two or three different group-V volatile elements, the crystallization was carried out from finite melt with a thickness of 0.5 mm at low (<560 °C) temperatures. X-ray microanalysis and X-ray diffraction were used to determine the composition, lattice mismatch, and crystalline quality of the epitaxial layers. The morphology and surface roughness were examined by atomic force microscopy. Surface photovoltage (SPV) spectroscopy at room temperature was applied to study the optical absorption properties and the photocarrier transport in the samples. The long-wavelength photosensitivity of the GaAsSbN and GaAsSb layers, determined from their SPV spectra, is extended down to 1.2 eV. Although GaAsSb has a slightly larger lattice mismatch with the GaAs substrate compared to GaAsSbN, it presents a higher photoresponse, since, in GaAsSbN, the incorporation of N induces additional recombination centres. Therefore, GaAsSb could be an alternative to GaAsSbN for solar cell applications

A Modular Method for the Calculation of Transmission and Reflection in Multilayered Structures

We describe a new modular method for the calculation of wave propagation in stratified media based on the direct use of reflection and transmission coefficients. Within this reflection from the left, transmission, and reflection from the right (LTR) method we define addition and multiplication operators that enable the theoretical construction of any multilayered structures from substructures. This modular concept allows for the design and analysis of complex multilayer structures for optical devices. (C) 2001 Optical Society of America.</p

Surface photovoltage characterisation of metal halide perovskite on c-SI using kelvin probe force microscopy and metal-insulator-semiconductor configuration

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Simulating experimental techniques : Kelvin Probe Force Microscopy NanoTexnology-NN22

International audienceKelvin Force Probe Microscopy (KPFM) is a local scale advanced characterisation technique derived from atomic force microscopy, and is the focus of much research interest. It allows measurement of the contact potential of a surface with a resolution of the order of nanometres, yielding high resolution surface work function maps. Analysis of these maps allows the extraction of information on the electronic band structure and transport properties of materials and interfaces at the local scale. The technique is however highly sensitive to surface properties and in particular to surface state distributions. Therefore, the interpretation of contact potential variations across material and doping interfaces is complex.This paper presents a review of the field of KPFM methods and their analysis by modelling techniques. We review analytical approximations in a first approach for understanding of the physics of the KPFM technique and its interpretation. We then progress to more advanced KPFM modelling, which involves simulating the two-dimensional KPFM scanning process by sequentially scanning the atomic probe across the surface thereby reproducing the spatial extent of the experimental method. The two-dimensional description allows the inclusion of atomic probe geometry and the resulting impact on the resolution. The numerical methods allow a description of surface defect properties in terms of distributions in the gap, as well as descriptions of dopant species in terms of their energy distributions and capture cross sections or lifetimes.Applications of these methods are considered with a focus on photovoltaic applications, for the dominant materials in the field including group IV, III-V and concluding with considerations for emerging materials such as perovskites

Surface photovoltage study of metal halide perovskites deposited directly on crystalline silicon

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