In this paper the electrical characteristics of metal–insulator–semiconductor (MIS) and metal–insulator–semiconductor–insulator–metal (MISIM) capacitors with (100)-oriented p-type silicon as a substrate under different high-$k$ gate dielectrics (SiO$_2$, HfO$_2$, La$_2$O$_3$ and TiO$_2$) are investigated in the semi-classical and quantum mechanical models. We review the quantum correction in the inversion layer charge density for p-doped structures. The purpose of this paper is to point out the differences between the semi-classical and quantum mechanical charge descriptions at the insulator–semiconductor interface and the effect of the type of oxide and their position (gate oxide or buried oxide) in our structures. In particular, capacitance–voltage ($C–V$), relative position of the sub-band energies and their wavefunctions are studied to examine qualitatively and quantitatively the electron states and charging mechanisms in our devices. We find that parameters such as threshold voltage and device trans-conductance are enormously sensitive to the proper treatment of quantization effects.

In order to improve photovoltaic efficiency, researches have been carried out on silicon nanowires (SiNWs). In this article, we report a comparative study between silicon substrate (Si) and SiNWs developed by a metal-assisted chemical etching (Ag) method at different etching times (25, 10 and 5 min). Scanning electron microscopy (SEM), transmission electron microscopy and X-ray diffraction were used to collect the morphological and structural informationon the SiNWs. Raman spectroscopy shows that the intensity of the nanowires is 4 to 10 times higher than that of the substrate, and increases with increase in etching time. The total reflectance of SiNWs reduced to less than 5% over theentire visible range. The low reflectance and zero transmittance of SiNWs lead to higher absorbance in the visible wavelength range. The SiNW-etched nanowire structure (25 min) works best for capturing light, we believe that having longer nanowires improves the optical working of the nanostructures and may be a potential candidate for high efficiency photovoltaic solar cells and other optic devices.