InGaP, a promising material for tandem solar cells

Abstract

In_1−xGa_xP can be used as a material for wide bandgap solar cells. The photovoltaic quality of In_1−xGa_xP is better than that of Al_1−xGa_xAs, which is used mostly in GaAs based tandem solar cells. This paper describes the MOCVD growth and characterization of In_1−xGa_xP epi on GaAs. Perfectly lattice matched In_1−xGa_xP epilayers have been obtained at different growth temperatures. These lattice matched layers exhibited excellent optical and electrical properties. Photoluminescence measurements at 4K resulted in a F.W.H.M. of 9.0 meV while Hall — v.d. Pauw measurements of the undoped layers gave mobilities of 6000 cm²V⁻¹sec⁻¹, the best value reported in literature sofar. The lattice matched layers have been doped n- and p-type over a wide carrier concentration range. Prelimenary results on In_1−xGa_xP solar cells indicate an efficiency of 4.5 % (AM1.5). Improvement of this efficiency may be attained easily.