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) 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 non-radiative 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 trap-assisted recombination process. Furthermore, such order of magnitude was confirmed by time-resolved photoluminescence measurements.