Liquid-phase epitaxy of AlxGa1-xAs and technology for tandem solar cell application

AlxGa1-xAs structures having a wide range of Al-content 0 < x < 0.5 and layer thicknesses up to 100 mu m were investigated. Solar cells were fabricated for the application as a top cell in an AlGaAs-Si tandem concentrator configuration. An Al-graded n-AlxGa1-xAs base layer was grown on a GaAs substrate by the liquid-phase epitaxy (LPE) cooling technique and was characterised by several methods. The LPE-ER (etchback-regrowth) process was used for the fabrication of a p-AlxGa1-xAs emitter and the growth of a p-AlyGa1-yAs (y > x) window-emitter layer for surface passivation. An AlGaAs selective etching process (including in situ monitoring) for the removal of the GaAs substrate was developed. The first Al0.26Ga0.74As top solar cells were produced.