"Effect of Solution Concentration on Optical and Morphological Properties of Gallium Nitride Thin Films "

Abstract

"The e.ects of precursor concentration on the structural, morphological, and optical properties of galium nitride thin films were studied. The films were prepared by depositing solutions with two di.erent precursor concentrations on quartz, p-type Si (100), and porous silicon substrates using the chemical spray pyrolysis technique. Gallium nitrate hydrate (Ga(NO3 )3 x H2 O) powder dissolved in ethanol was used as the gallium source. Morphological, structural, optical, and spectral properties of the deposited films were characterized by atomic force microscopy, X-ray di.raction, Raman spectroscopy, photoluminescence, and ultraviolet–visable spectrophotometry. The X-ray di.raction results showed a hexagonal structure with orientation normal to the (004) plane. The optical bandgap decreased from 3.17 eV to 3.1 eV when the precursor concentration increased. The results from atomic force microscopy demonstrated that the grain sizes increased from 35 nm to 50 nm when the concentration increased. The root-mean-square also increased, from 9.666 nm to 12.4 nm, as the concentration increased. Blue photoluminescence of gallium nitride was detected in the range from 380 nm to 480 nm and Raman results showed a peak centered at 710 cm . 1 , consistent with the GaN longitudinal optical phonon "