Optical absorption and thermal conductivity of GaAsPN absorbers grown on GaP in view of their use in multijunction solar cells

•As content strongly modified the optical absorption spectrum of GaAsPN.•The optical absorption of GaAsPN absorbers is evaluated with PDS for various growth and annealing conditions.•Thermal conductivity of GaAsPN absorbers is measured for various growth and annealing conditions.

The optical absorption and thermal conductivity of GaAsPN absorbers are investigated by means of optical absorption spectroscopy and photo-thermal deflection spectroscopy (PDS) for different 100 nm-thick GaAsNP/GaP samples under different growth conditions and various post-growth annealing temperatures. It is first shown that the As content strongly modifies the optical absorption spectrum of the GaAsPN: with a maximum absorption coefficient of 38,000 cm−1 below the GaP bandgap energy. The optical absorption and thermal conductivities of the samples are then evaluated for various growth and annealing conditions using PDS: the results showing overall agreement with optical absorption spectroscopy measurements. A significant improvement in optical absorption and thermal conductivity after annealing is demonstrated. The best thermal conductivity measured is equal to 4 W/m K. These results are promising for the development of absorbers in multijunction solar-cell architecture.