Comparative study of structural and visible luminescence properties of AZO thin film deposited on GaAs and porous GaAs substrates

• Al-doped ZnO (AZO) thin films were deposited on GaAs and porous GaAs substrates using RF magnetron sputtering.
• AZO films show predominant a-axis orientation.
• Porosity of GaAs substrate enhances arsenic diffusion into the film.
• Porosity of GaAs substrate enhances the visible luminescence Of AZO film.

The objective of this study is to investigate the effect of the pre-treatment of GaAs substrate by making it porous on structural and visible luminescence properties of aluminum - doped zinc oxide (AZO) thin films deposited by the use of a radio frequency magnetron sputtering. Porous GaAs has been prepared by anodic etching of n+-type (100) GaAs wafers in a HF:C2H5OH:HCl:H2O2:H2O electrolyte. Structural and visible luminescence properties of deposited films have been investigated by means of x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and room temperature photoluminescence (PL) spectroscopy. XRD patterns of deposited films show predominant orientation along (100) crystal plane of hexagonal ZnO. A diffraction peak due to cubic zinc arsenide (Zn3As2) is only observed in the XRD pattern of the film deposited on porous GaAs. XPS results further confirm that the AZO film deposited on porous GaAs is doped with arsenic (As). This is attributed to the enhancement of As diffusion into the film due to nanostructure nature of porous GaAs. The use of porous GaAs as a substrate also leads to an enhancement of the visible PL intensity of the deposited film. This is found to have a strong relationship with the change in the content of zinc and oxygen related defects in the film as it is revealed from peak analysis of XPS and PL spectra.