Dislocation effect upon the efficiency of single-crystal thin-film AlGaAs-GaAs heteroface solar cells on Si substrates is analyzed. Solar-cell properties are calculated based on a simple model; in the model, dislocations act as recombination centers to reduce the minority-carrier diffusion length in each layer and increase the space-charge layer recombination current. Numerical analysis is also carried out to optimize thin-film AlGaAs-GaAs heteroface solar-cell structures. The fabrication of thin-film AlGaAs-GaAs heteroface solar cells with a practical efficiency larger than 18% on Si substrates appears possible if the dislocation density in the thin-film GaAs layer is less than 106 cm−2.

A double hetero (DH) GaAs tunnel diode which consists of a GaAs tunnel junction sandwiched between Al x Ga1-x As layers has been grown by molecular beam epitaxy, and its annealing characteristics studied. DH tunnel diodes have the advantage that a decrease in the tunnel peak current density due to annealing is greatly suppressed compared to conventional GaAs diodes without AlGaAs layers. In-depth profiles of dopants indicate that the AlGaAs layers act as blocking layers against Be diffusion, which causes a degradation of the diodes. An Al0.4Ga0.6As/GaAs tandem solar cell incorporating the DH tunnel junction as interconnectors has achieved a conversion efficiency of 20%.

This paper describes some recent developments in GaAs thin-film solar cells fabricated on Si substrates by metalorganic chemical vapor deposition and numerically analyzes them.GaAs solar cells with efficiency of more than 18% are successfully fabricated on Si substrates by reducing the dislocation density. Photovoltaic properties of GaAs/Si cells are analyzed by considering the effect of nonuniform dislocation distribution on recombination properties of GaAs thin films on Si substrates. Numerical analysis shows that the effect of majority-carrier trapping must be considered. High efficiency GaAs solar cells with total-area efficiency of over 20% on Si substrates can be realized if dislocation density can be reduced to less than 5×105 cm−2.

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As a next step the PMD compensator was inserted. The controller maximised the 25 and 4OGHz power levels. The autocorrelation trace reveals a slightly narrower pulse with a deconvolved 5. 2~s width (Fig. 2). Similar pulse peaking has already been found in NRZ experiments [3, 6, 81. Then the emulator was Development of the modelocked laser was funded in ACTS project ESTHER and "I-Project (Univ. Paderborn).