Vapor-grown InGaP/GaAs solar cells

GaAs solar cells with conversion efficiencies as high as 14% at AM1 have been grown by the GaCl/AsH3 hydride technique. Thin (∼200 Å) layers of InGaP were used to passivate the GaAs top surface. We observe a 70-fold increase in photoluminescence intensity of the GaAs after passivation, which is consistent with a lowering of the GaAs surface recombination velocity from ≳106 to <104 cm/sec. Short-circuit current densities (Jsc) as high as 22 mA/cm2 and open-circuit voltages as high as 0.96 V were observed. (If achieved together, those values would yield an efficiency of almost 18%.) Voc was observed to increase directly with p-layer thickness (t), whereas Jsc decreased directly with t. The efficiency also increased as the zinc doping was decreased.