Generation and collection of photocarriers in dilute nitride GaInNAsSb solar cells

An improved photocurrent production is demonstrated in dilute nitride GaInNAsSb solar cells grown by molecular beam epitaxy. The photovoltaic properties were investigated by increasing the thickness of GaInNAsSb layers from 1.0 to 3.0 µm. The amount of photon absorption increased with increasing thickness. Yet an incomplete photocarrier collection was observed in the 2.0‐ and 3.0‐µm‐thick GaInNAsSb devices. This feature is due to a partial lack of electric field in the GaInNAsSb region. In order for complete carrier collection aided by the electric field, the background‐doping level should be as low as ~1014 cm−3 in a thick undoped‐GaInNAsSb absorption layer. Here, the effectiveness of annealing on improving the field‐assisted carrier collection is shown. This is ascribed to a decrease of the background doping in the GaInNAsSb layer. In a properly designed device for a 1.0‐eV GaInNAsSb cell, it is demonstrated that the external quantum efficiency can reach as high as 90% at wavelengths longer than the GaAs bandgap. Copyright © 2015 John Wiley & Sons, Ltd. We focused on improving both the generation and the collection of photocarriers in the GaInNAsSb solar cells. A set of GaInNAsSb‐based single junction solar cells with increased thicknesses was fabricated, and then the photovoltaic properties were investigated. We demonstrated the reasonably high carrier collection properties in 1.0 eV GaInNAsSb solar cell, which gives a GaAs‐filtered current density of 12.2 mA/cm2. This is a 47% enhancement of the JSC value compared to our past report.