Crystallographic and optical characterizations of Ag(Ga,Al)Te₂ layers grown on c -plane sapphire substrates by closed space sublimation

Ag(Ga,Al)Te₂ layers were grown by the closed space sublimation method on c -plane sapphire substrates. The source used was AgAlTe₂/AgGaTe₂ mixture or AgAlTe₂/Ga₂Te₃ mixture. The crystallographic property of Ag(Ga,Al)Te₂ layers was analyzed by X-ray diffraction (XRD). XRD spectra of layers exhibited very strong 112 diffraction peaks regardless of the variation of the source material mixture. In addition to crystallographic characterizations, optical properties of the Ag(Ga,Al)Te₂ layer were evaluated through transmittance measurements. The bandgap energy was decreased when the source mole ratio of Al to Ga was decreased. It was revealed that control regulation of x composition of Ag(Ga_1-x,Al_x)Te₂ was feasible by varying the source mole ratio Al/(Ga+Al).