Investigation of opto-electronic properties on gradient-porosity porous silicon layer

An Investigation of Multi-Porous Silicon Gas Sensor

“…The formation of this complex structure was occurred in the high-range of porous silicon formation. The distance between the pore-like structure regions for (mPsi) sample etched at two etching steps is in the range (1-3)µm while for (mPsi) sample etched at four etching steps it is a bout (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)µm. This increase in the width of thetrenches could have been resulted as a result of the illumination intensity increase.…”

“…The use of porous instead of planar silicon as substrate material provides many advantages due to the large surface to volume ratio that can reach 500m 2 / cm -3 . The porous silicon /silicon substrate junction had been used for sensing applications as gas sensors based upon the increase in current due to the dipole moment of the gas [4,5]or due to charges trapped on the dangling bonds associated with the silicon /porous silicon interface [6].In previousstudies,(Psi) porosity gradient was discussed primarily as artifacts in standard constantcurrent etching [7],as a characterization tool for optoelectronics studies [8] and for optical filter applications [9] and also for silicon solar cell applications as an antireflection coating [10].In the present work,the properties of amulti-porous silicon layer (mPSi)used as gas sensor by fabricating(Au/mPSi/n-Si/Au) sandwich structures is investigated. The electrical response of this sensorisdiscussed based on the analysis of the surface morphology of the (mPSi) by mean of SEM micro images.…”

Nanocrystalline Porous Silicon: Structural, Optical, Electrical and Photovoltaic Properties

“…It suggests that the energy band gap of NPS is similar to the energy band gap of silicon substrate or well, the contribution of the NPS to the photovoltaic effect is negligible. The absence of photocurrent from the NPS layer is attributed to the recombination of charge carriers due to the dangling bonds (Hwang et al, 2011). An energy diagram for NPS from p-Si (Fig.…”

Gradient-Porosity Porous Silicon (GPSi) as Anti-reflection Coating in Solar Cells Applications

“…1(b)] resulting in a lower broadband reflectivity. Very low narrow band reflectivity can also be achieved by exploiting the interference of light reflected from the two interfaces [6]. Further reduction in broadband reflectivity can be achieved by adding additional intermediate index layers, thus breaking the air-silicon index discontinuity into smaller and smaller steps [7].…”

“…This relatively high reflectivity of silicon solar cell in the (400 nm -850 nm) spectral range is due to the large reflective index discontinuity that exists at the air-silicon interface. Figure (6) shows the reflectivity for porous sample which prepared at illumination intensity of (50 mw/cm 2 ) with (405 nm) blue laser diode wavelength. As shown in this figure, it can be seen that the reflectivity of porous silicon surface is much lower than that of silicon surface (reference sample).…”