Violet and orange luminescence from Ge-implanted SiO2 layers

Ge ions of 100 keV were implanted into a 120-nm thick SiO2 layer at room temperature (RT), 300, and 500°C. The employed doses of Ge ion were 5×1015, 1×1016, 5×1016, and 1×1017 cm−2. Maximum intensity of sharp violet photoluminescence (PL) from the sample implanted at room temperature with a dose of 1×1016 cm−2 is observed after the sample has been annealed at 500°C for 2 h. Broad orange luminescence is also shown in hot-implanted samples besides the violet. Both are known as defect-related luminescences. As observed by current-voltage (I–V) characteristics, the defect-related samples exhibit large leakage currents with electoluminescence (EL) at only reverse bias region while a nanocrystal-related sample obtained by an annealing at 1100°C for 4 h shows the leakages at both the reverse and the forward region. The carrier-transport and EL mechanisms are explained from the PL and I–V results.