Electrical Properties of Metal-Porous GaAs Structure at Water Adsorption

This paper reports the morphological, optical, luminescent and electrical properties of electrochemically made porous GaAs in order to evaluate their humidity sensing performance. The obtained porous GaAs exhibits non-homogenous surface morphology, which consists of pyramid-shaped crystallites and micropores. Photoluminescent and FTIR study shows that the surface of such material is covered by an oxide of As and Ga. The impedance spectroscopy was applied to analyze the influence of water vapor on electrical properties of metal-porous GaAs. It was shown that water adsorption results in the Nyquist plots shift to the region of higher frequencies. In humid atmosphere resistance Rv and characteristic time of charge accumulation τ are decreased by 1.4 times and 5 times, respectively; resistance Rb and capacity Cb decreased by 1.4 times and 4.4 times, respectively. The response of the metal-porous GaAs structure to the adsorption of water is attributed to the decreasing of the bulk resistivity and potential barrier height. The formed oxide layer on the surface of porous GaAs plays a dual role—it increases the ability to adsorb water molecules and prevents the surface from receiving structural degradation.