Near infra-red photoluminescence of Nd3+ in hydrogenated amorphous silicon sub-nitrides a-SiNx:H⟨Nd⟩

Neodymium-doped hydrogenated amorphous silicon sub-nitrides a-SiNx:H(Nd) thin films were deposited by rf-sputtering using a Si target partially covered by metallic Nd chips and Ar + N-2 + H-2 sputtering gas. Characteristic Nd3+ near infra-red (NIR) photoluminescence (PL) was detected between 10 and 300 K with peaks at similar to935, similar to1090 and similar to1390nm, corresponding to the intra-4f transitions F-4(3/2) --> I-4(9/2), F-4(3/2) --> I-4(11/2) and F-4(3/2) --> I-4(13/2), respectively. Measurements using different excitation wavelengths indicate that the Nd3+ excitation occurs through the a-SiNx:H matrix. Varying the nitrogen content x from 0 to nearly 1.3 increases the matrix bandgap. The PL efficiency is maximum when the bandgap corresponds to twice the F-4(3/2) --> I-4(9/2) transition, indicating a defect-related energy transfer mechanism. The temperature quenching can be as low as less than a factor 3 between 10 and 300 K for 2.8 eV gap samples. Thermal annealing can enhance the PL intensity by a factor 10. Neodymium concentrations above similar to3 x 10(20) atoms/cm(3) slightly reduce the PL intensity probably due to excess of inactive defect centers. Along with erbium-doped amorphous silicon alloys, a-SiNx:H(Nd) can be used in the development of photonic devices in the future. (C) 2003 Published by Elsevier B.V.