Structural, optical and electrical characterization of nanostructured porous silicon: Effect of current density

• Fabrication of porous silicon (PS) samples using p-type crystalline silicon wafers by electrochemical anodization method.
• The influence of the higher current density on silicon wafer is analyzed to understand the electrical transport properties.
• Electrical properties of PS based heterojunction device was analyzed and it proves suitable material for sensor and diode.
• The efficient rectification properties of PS were found under dark.
• The experimental studies concluded that the high etching process plays an important role on structural features of PS.

In this work, an attempt has been made to fabricate porous silicon (PS) from p-type crystalline silicon (c-Si) wafers by using the electrochemical etching process at six different current densities (40, 60, 75, 100, 125 and 150 mA/cm2) with constant time (30 min). The influence of varying current density on morphological, structural, optical and electrical properties of PS samples were analyzed by using SEM, AFM, XRD, FT-IR, PL and electrical (I–V) techniques, respectively. Microstructural images clearly showed that the average pore diameter and thickness increase with increase current densities up to 100 mA/cm2 and decrease for 125 mA/cm2. It could be related to breaking of pore walls and exposing to the next layer of c-Si. Further increase the current density about 150 mA/cm2, the average pore diameter increase as in the case of first layer (40–100 mA/cm2) of c-Si wafer. The result is reflected in PL emission band (at 708 nm) and the intensity of the emission band shifted towards red region. The X-ray diffraction pattern confirm the formation of porous silicon as appeared as a broad peak at 2θ = 69.3° belongs to (4 0 0) reflection. The FTIR study supports the X-ray diffraction analysis that shows the vibrational bands of S–H2 and Si–O–Si at 2109 cm−1, 915 cm−1 and 615 cm−1 and 1107 cm−1, respectively. The I–V characteristic of PS exhibited rectifying behavior with different values of ideality factor (η) and barrier height (ϕb). It is concluded from the experimental results that the formed pores developed up to 100 mA/cm2 in the top layer of c-Si and the formed pores exposed to the next layer of c-Si when increase the high electrochemical etching process (above 100 mA/cm2).

Fabrication of porous silicon (PS) layers by electrochemical anodization method. Structural, optical and electrical properties of the PS samples were analyzed.Figure optionsDownload as PowerPoint slide