Nitrogen-related defects and their effect on the electrical properties of GaAsN grown by chemical beam epitaxy

Two nitrogen-related lattice defects were confirmed in GaAsN grown by chemical beam epitaxy (CBE), using deep level transient spectroscopy (DLTS). The first defect is a non-radiative recombination center (E1), with average activation energy of 0.33 eV below the conduction band minimum (CBM) of GaAsN. The lifetime of electrons from the CBM to E1 was calculated to around ~0.2 ns, using the Shockley-Read-Hall (SRH) model for generation-recombination. These results expected E1 as the main cause of short minority carrier lifetime in GaAsN films. The Second defect is a hole trap (H2), deep acceptor-like state, with average activation energy of 0.15 eV above the valence band maximum (VBM), and originates from the N-H bond. Its density was found to be in good relationship with free hole concentration in p-type films, which were grown under N and H rich growth conditions. This deep acceptor was suggested to be the main cause of high background doping in GaAsN, which prevents the design of a wide depletion region GaAsN based solar cells and drops the minority carrier lifetime.