Analysis of Current Transport Mechanisms in GaAsN Homojunction Solar Cell Grown by Chemical Beam Epitaxy

Current transport mechanisms were investigated in a GaAsN homojunction solar cell (HJSC) grown by chemical beam epitaxy. At each temperature of measurement, the current-voltage ( I-V-T) characteristics were found to deviate from the diffusion model. The fitting of these characteristics affirmed that the recombination current in the space-charge region of the HJSC is mainly attributed to a localized state at 0.31 eV below the bottom edge of the conduction band of GaAsN. This recombination center was identified by deep-level transient spectroscopy. It was previously confirmed to act as a nitrogen-related nonradiative recombination center, and the split interstitial formed from one nitrogen atom and one arsenic atom in a single V-site (N-As)_As was tentatively suggested to be its possible origin. The lifetime of electrons from the conduction band to its energy level was calculated to be around ~0.20 ns, using the Shockley-Read-Hall model for a trap-assisted recombination process. Furthermore, such order of magnitude was confirmed by time-resolved photoluminescence measurements.