Strain issues in stress compensated QDs for intermediate band solar cells

Abstract

Trabajo presentado al "25th European Photovoltaic Solar Energy Conference and Exhibition" y al "5th World Conference on Photovoltaic Energy Conversion", celebrados en Valencia (España) del 6 al 10 de Septiembre de 2010.In this work we have investigated several problems that may appear during the growth of strain balanced quantum dots for high efficiency solar cells. We have used in situ stress measurements to evaluate the total stress introduced by the InAs quantum dots and the exact composition and thickness of the GaAsP stress compensating barrier. We have found that the quality of perfectly balanced samples can degrade as we stack the quantum dot layers (even for a reduced number of them) leading, eventually, to a complete suppression of the quantum dot formation. We attribute this effect to a strong strain modulation at the surface of the sample that leads to the migration of phosphorus adatoms away from the top of the quantum dots, increasing the inhomogeneity of the compensating barrier. We conclude that using a pure binary material as compensating layer would prevent this decomposition and lead to better material quality.Peer Reviewe