Development of indium-rich InGaN epilayers for integrated tandem solar cells

InGaN epilayers have been investigated for use in photovoltaic solar cells for the past years. At present, almost all photovoltaic device structures reported have exhibited very low short circuit currents and thus very low solar conversion efficiency. This phenomenon has been attributed to point and extended defect chemistry in InGaN epilayers (e.g. vacancies, misfit dislocations, and V-defects), as well as to spinodal decomposition of the strained InGaN wurtzite lattice system. These defects become more dominant for higher indium concentration InGaN epilayers needed for multijunction photovoltaic device structures. In this work, we will report on the growth and characterization of indium-rich InGaN epilayers that have been grown by novel MOCVD growth technology, including the growth at superatmospheric reactor pressures.