Nanostructurale nature of the porous GaAs layer formed on p+-GaAs substrate by electrochemical anodization
A porous GaAs layer has been formed by electrochemical anodization in HF based solution on extremely doped p-type GaAs substrate. Porous nature of the elaborated sample has been evidenced by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Nanostructurale nature of the porous layer has been demonstrated by X-ray diffraction analysis (XRD) and confirmed by photoluminescence spectroscopy (PL).
Synthesis Porous GaN by Using UV-assisted Electrochemical Etching and Its Optical Studies
The PL of porous GaN sample shows higher intensity with smaller FWHM and red-shifting relative to the as-grown sample. The energy gap for porous GaN sample was smaller compare to the as-grown sample. The SEM surface image of UV-assisted electrochemical etching process is shown a shape and size of pore which was formed on the surface of the GaN, therefore the shape of pores formed was in spherical shape. The size of the pores formed has diameter as small as 85 nm. Two PL peaks were observed in the as-grown and porous GaN sample. For the as-grown GaN, the higher peak was observed at “361.946 nm” and the other at “723.739 nm” which is in UV and red luminescence region respectively. The FWHM is “8.198 nm” at “361.946 nm”. For the porous GaN, the higher peak was observed at “364.235 nm” and at “728.039 nm”, so their FWHM are “4.244 nm” and “8.926 nm” respectively. The peaks of porous sample were red-shifted at “2.289 nm and 4.30 nm” respectively compare to the peaks of the as-grown GaN. PL intensity of the porous samples was observed to be increased. Raman peaks representative to the wurtzite GaN crystal, namely E 2 (low) at 142.426 cm -1 , E 2 (high) at 568.771 cm -1 , and A 1 (LO) at 736.769 cm -1 were clearly observed.
Pore morphology and the mechanism of pore formation in n-type silicon
Porous layers formed in n‐type silicon are characterized by pores of square cross section oriented perpendicular to the (100) plane. The pore walls are defined by the {011} planes in the [100] zone with secondary pores propagating from the main pores in the 〈010〉 and 〈001〉 directions. The pores are located in an array with a characteristic spacing. The characteristic pore morphology during stable pore propagation is explained in terms of a tunneling mechanism due to a high‐field region created by the curvature at the pore front. The pore spacing is determined by the distance at which the region between the pores becomes fully depleted.