Photoluminescence, morphological and electrical properties of porous silicon formulated with different HNO3 concentrations

In this study, porous silicon (PS) with observable luminescence was fabricated on p-type Si (1 0 0) substrate by wet chemical etching with the mixture of HF and different HNO3 concentrations in the ratio of 1:100. The porosity of PS shows dependent on HNO3 concentration. SEM images exhibit the average pore size increases with the increasing of HNO3 concentration. The emission of PS was characterized by photoluminescence (PL) spectroscopy. The PS is able to emit orange-red visible PL under UV illumination with the peak falls within the wavelength region of (620-660) nm. Brighter emission is observed on PS etched at higher HNO3 concentration, and the emission peak shifts to shorter wavelength when the energy gap and surface roughness increase. The calculated band gaps are lied in the range of (1.90-2.00) eV, which is higher than Si. Moreover, the surface conductivity decreases as the PS energy gap increases.