Effects of temperature, nitrogen ions, and antimony on wide depletion width GaInNAs

Abstract

GaInNAs is a promising candidate material to increase the conversion efficiency of triple junction solar cells, but the dilute nitrides suffer from low-to-nonexistent minority-carrier diffusion lengths. The use of molecular beam epitaxy grown p-i-n structures with wide depletion widths can achieve high photocurrents in dilute nitrides, but this requires background doping below 2×1014cm−3 in the i layer. Here, the authors report on a number of factors that increase the net background acceptor concentration, hindering the effects to realize wide depletion widths, including high substrate temperatures, ions from the rf plasma source used to provide active nitrogen, and the addition of Sb. In addition, low substrate temperatures lead to an increase in n-type conductivity. Solar cell results that show the deleterious effects of Sb on GaInNAs devices are presented, including decreased open-circuit voltage and fill factor.