Broadband near-infrared luminescence of porous silicon heat-treating at high temperature

The influence of the annealing temperature on the Photoluminescence (PL) of hydrofluoric-treated Porous Silicon (PSi) films prepared at the same current densities has been investigated. The PSi was annealed at between 800 and 1,100°C in air and then the samples were re-annealed in N₂ at the higher temperature of 1,300°C. Oxidized PSi shows very broad near-infrared luminescence. The PL intensity and the peak position strongly depend on the annealing temperature. The PL peak first blue shifts from 850°C drastically, and then red shifts gradually from the annealing temperature at 1,000°C. After re-annealing in N₂ at 1,300°C, a broad and long wavelength near-infrared luminescence peak at around 1,130 nm was observed in the PSi-N₂, and the PL peak was red shifted. This is due to the high degree oxidized Si⁴⁺ state decreasing to three suboxide states, Si¹⁺, Si²⁺, or Si³⁺, when annealing at high temperature in the N₂ atmosphere.