Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 55: Photovoltaics: mainly Technology and Photon Management

HL 55.7: Talk

Wednesday, March 16, 2011, 16:15–16:30, FOE Anorg

Time Resolved Measurement of Interface and Bulk Recombination of Solar Cell Materials — Anja Dobrich, •Nadine Szabó, Klaus Schwarzburg, and Thomas Hannappel — Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany

Today's state-of-the-art multi-junction solar cells are based on III-V semiconductor compounds grown by MOVPE. The current record multi junction solar cell grown on germanium, having Ge, Ga(In)As and GaInP subcells, have reached a record efficiency of 41.6%. This could be improved further if the low bandgap Ge subcell would be replaced by a more efficient double junction solar cell. For this purpose the low bandgap absorbers InGaAs and InGaAsP grown lattice-matched on InP(100) are suitable. Due to the enhanced bandgap composition a better yield of the solar spectrum is feasible.

Here, we study how the preparation routine of the critical InGaAs to InP interface effects the spatial homogeneity. As a probe for bulk and interface defects time resolved photoluminescence (TRPL) was used. For the lifetime measurements we have grown double hetero (DH) test structures. Due to the arsenic carry over in the InP layer, the InGaAs/InP interface is well-known to be critical with respect to the quality of the interface. The interfaces were prepared via different preparation routes starting with either III- or V-rich InGaAs surface terminations. In order to evaluate the interface formation we analysed the surface reconstruction in situ with reflection difference (RD) spectroscopy and via a contamination-free transfer to UHV with LEED.