EMRP-ENG51: Metrology for III-V materials based high efficiency multi-junctions solar cells (SolCell)

• Unité de recherche: METAS
• Numéro de projet: F-5217.30035
• Titre du projet anglais: EMRP-ENG51: Metrology for III-V materials based high efficiency multi-junctions solar cells (SolCell)

Mots-clé (Anglais)

III-V semiconductors, multi-junction solar cell, reference material, photovoltaic, electrical transport, metrology, efficiency, heterostructure properties, quantum dots, spectral responsivity, standardisation

Description succincte (Anglais)

The overall aim of this JRP is to develop traceable metrological infrastructure in support of the rapid advances made on multi-junction solar cells that are based on III-V materials. The JRP will develop techniques and methodologies to enable the traceable and accurate characterisation of structural, optical, electrical, optoelectronic and thermionic properties of III-V material based MJSC, from the macro to nanoscale, in order to enhance the efficiency of the current devices and enable the production of the next generation solar cells.

This project is part of the European Metrology Research Programme (EMRP, http://www.euramet.org/index.php?id=emrp); it is partly funded by the European Union on the basis of Decision No 912/2009/EC.

A more detailed description of the project may be found in the encloed publishable summary.

Documents annexés

• ENG51_Publishable_JRP_Summary.pdf [PDF] 132 kB

Objectifs du projet (Anglais)

The scientific and technical objectives are:

• To develop methods to accurately measure electrical transport properties of III-V complex heterostructures: band-gap, work function, dopant distribution, photocurrent, carrier density, diffusion length, doping dependent minority carrier lifetime, absorption coefficients and series-resistances. Accurate measurements of these physical parameters are particularly important to understand the electrical transport phenomena in these heterostructures (WP1, WP3);
• To characterise composition, thickness, structural and optical properties of III-V material in order to highlight the effect of defects concentration, microstructure and interfaces on the recombination mechanisms of charge carriers (WP1, WP3);
• To measure carrier transport between interfaces in MJSC and to characterise narrow tunnel-junction properties (WP1);
• To develop reliable tools and workflows to measure size dependent electronic structures of nanostructured semiconductor quantum dots (WP3)
• To measure thermoelectric properties of III-V materials and thermal transport across interfaces (WP3);
• To develop traceable and reliable calibration methods and standards for determining device efficiency, linearity, temperature dependence and spectral responsivity of MJSC devices (WP2).

METAS is involved in WP2 and WP3.

Résumé des résultats (Abstract) (Anglais)

The technical deliverables were all about determining dopant densities with 50 nm resolution in III-V samples geared towards solar cell applications. Here, multi-junction solar cells and quantum dot based solar cells were in the focus.

In order to reach these objectives:

• METAS developed design specifications for various test samples fabricated by collaborators within the project.
• The SMM’s spatial resolution was demonstrated to be ~50 nm by scanning a tunnel junction.
• A wide range of different samples has been measured (multilayer/-junctions samples, quantum dots, etc.).
• In collaboration with METAS’ AFM group, the topography of a quantum dot sample has been determined. Demonstrating its degradation and the need for new, clean samples.

The major outcome of the project is a versatile calibration routine to determine carrier densities being functional even on GaAs. The results obtained compare well with reference method SIMS (Secondary Ion Mass Spectrometry) and the algorithm is also universally applicable to different SMM setups within a wide frequency range.

In the course of the project, general SMM improvements to meet technical challenges regarding spatial resolution and sensitivity had to be achieved:

• Microscope head, electric circuits for impedance matching and the sample holder were completely redesigned.
• The SMM’s self-written control software was revised and extended.
• A new sample preparation routine, which is generally applicable also for future pro-jects, was introduced.

Mise en oeuvre et application (Anglais)

The calibration sample, which was designed together with LAAS, LNE, Keysight and NPL to develop a calibration algorithm will be produced and made commercially available by LNE. A prototype is already available to METAS.

The developed calibration algorithm for the SMM will be used in follow-up projects and can be used in future customer calibrations provided that the SMM is equipped with a shielded tip. The calibration algorithm can be used by the wider SMM community because its instrument independency was demonstrated within the project.

Publications / Résultats (Anglais)

A. Buchter, J. Hoffmann, A. Delvallée, E. Brinciotti, D. Hapiuk, C. Licitra, K. Louarn, G. Almuneau, F. Piquemal, M. Zeier, F. Kienberger, Scanning Microwave Microscopy Applied to Semiconducting GaAs Structures, to be submitted