Strong infrared photoluminescence from black silicon made with femtosecond laser irradiation

Abstract

Strong infrared photoluminescence (PL) was observed for the first time from black Si (b-Si) formed by femtosecond laser irradiation and treated by rapid thermal annealing. The PL peak energy changes from 0.78 to 0.84 eV (1.59 to 1.48 μm) when increasing the annealing temperature from 500°C to 1200°C, showing a tunable property. Compared to those after annealing at 1000°C, both the peak intensity and the peak energy change slightly after annealing at higher temperatures of 1100°C and 1200°C, showing a high thermal stability of their structures and PL properties. With the x-ray photoelectron spectroscopy (XPS) results from the b-Si before and after etching in KOH solution, the PL is attributed to dislocation-related (D1) luminescence rather than sulfur-related impurity center luminescence. The integrated intensity of D1 PL as a function of excitation power can be fitted by I [proportionality] P(m) with m of 0.58, suggesting that the PL of the b-Si sample originates from the recombination of bound-to-bound states. The high thermal activation energy of 75.2 meV suggests a high quenching temperature of D1 PL, showing a potential of application at room temperature. This work may promote the progress of research on b-Si in the area of Si-based optoelectronics.