Deep level optical spectroscopy of GaN nanorods

Deep level defects in GaN nanorods (NRs) grown by metal organic chemical vapor deposition were studied using deep level optical spectroscopy (DLOS) and microphotoluminescence (μ-PL). DLOS determines the absolute optical ionization energy, discerns majority versus minority carrier photoemission, and has sensitivity to nonradiative defect centers. These are important aspects of deep level spectroscopy for NRs that are not obtainable using luminescence techniques alone. Deep level defects were observed via DLOS at Ec−2.81 eV, Ec−1.77 eV, and Ec−3.19 eV, where Ec is the conduction band minimum. The μ-PL spectra revealed a dominant defect band peaked near 2.19 eV. The Ec−2.81 eV band gap state and the 2.19 eV PL peak can be attributed to the same defect center within a one-dimensional configuration-coordinate model. The NR DLOS spectra are compared to reports for thin film GaN, and possible physical origins of the deep level defects are discussed.