The Suppression Effect of 830nm Laser Irradiation on Porous Silicon Formation

The suppression effect of 830nm laser irradiation is fuond on the formation of fine porous silicon, which used hydrofluoric acid (HF) containing electrolyte for electrochemical etching. The photoluminescence (PL) profile shows a single peak at 1.94 eV corresponding to red emission at room temperature. On the laser-irradiated surface, the suppression/etching rate was changed by the laser power. Our study shows that the suppression effect of laser irradiation on the porous silicon layer be considered to a feasible technology for fabricating a uniform sub-5 nm thick porous layer.The thickness of porous layer can be precisely controled by the intensity of laser power and etching time with a tolerance in minutes.

In the study, we used 5×5 cm², boron-doped, 1 to10 Ωcm, (100) Si specimens and the laser with wavelength of 830nm at maximum power of 5.0mW with beam size of 1.0mm. The laser institutional platform was added the polarizer to control the power of the laser beam.

The power of laser was adjusted to1.0mW, 2.0mW, 3.0mW, 4.0mW, and 5.0mW in air at room temperature. In Fig. a and b, the pictures show the suppression of formation of porous silicon by the 830nm laser at 3.0mW after electrochemical etching in HF solution with current of 100mA for 10 minutes. The thickness of porous silicon varies of  the outer region of laser-irradiated area could be observed by Field Emission Scanning Electron Microscope (FE-SEM).  A straight-line slope of a porous silicon layer between the laser irradiation and non-laser irradiation that confirms the size of Gaussian beam with the suppression phenomenon of porous silicon. We called the propagating out profie of a Gaussian beam in the laser irradiation is the transition zone of porous silicon formation (TZPS).