Optical and photoelectrical properties of β-FeSi₂ thin films

Absorption, photocurrent, and infrared reflectivity spectra of the polycrystalline β-FeSi₂ thin films in relation to the Si substrate temperature are presented. The photocurrent spectra involving both the fundamental interband, extrinsic defect transitions of β-FeSi₂ and the intrinsic transitions of Si substrates are observed. Both the absorption and photocurrent measurements show the direct gap nature. A simple recombination model is proposed to account for the photocurrent results. We show that better quality β-FeSi₂ films can be achieved at higher substrate temperature. The simplicity, sensitivity, and reliability of the photocurrent measurements for studying β-FeSi₂ are well demonstrated.