Comparison of dilute nitride growth on a single- and 8x4-inch multiwafer MOVPE system for solar cell applications

The dilute nitrides like (GaIn)(NAs) or Ga(NAsSb) are attractive materials for the next generation of photovoltaic cells with four to six active junctions. Unfortunately, these compounds suffer from a low minority carrier diffusion length. This can be partially compensated by choosing suitable device structures with a reduced prerequisite on the necessary current density. (GaIn)(NAs) solar cells with a bandgap between 1.0 and 1.2 eV have been grown by metal organic vapor-phase epitaxy on single- and 8 x 4-in multiwafer reactors. Short-circuit current densities up to 10.9 mA/cm(2) (AM0) have been achieved for a (GaIn)(NAs) cell filtered with GaAs. This excellent value is sufficient for the application in five- or six-junction photovoltaic cells. Challenges are resulting from the transfer of growth conditions to a production size multi-wafer MOVPE reactor, which are discussed in this paper. (C) 2004 Elsevier B.V. All rights reserved.