Investigation of growth temperature effects on SnSe-based photodetector performance

Abstract

SnSe thin films were synthesized by thermal evaporation on glass slides at elevated growth temperatures. The grown films were investigated in terms of structural, morphological and optical properties. Furthermore, electrical characteristics and time-dependent photoresponses of SnSe-based photodetectors were studied in depth. SnSe thin films showed orthorhombic crystal structure with a preferred orientation of (400) for the growth temperature of 150 °C. However, the preferential orientation changed from (400) to (111) with increasing of growth temperature to 200 °C. Top view SEM data displayed a porous morphology for the samples grown at 200 °C and 250 °C temperatures. More transparent SnSe films were obtained when the growth temperature was increased to 200 °C. The band gaps of SnSe sample deposited at 150 °C and 200 °C were determined to be 1.22 eV. However, band gap reduces to 1.06 eV with the increase of the substrate temperature to 250 °C. Raman data demonstrated the shift in the general peak positions to higher frequencies as the growth temperature is increased due to the variation in bond lengths between Sn and Se atoms. Photocurrent-time data showed that SnSe sample grown at a growth temperature of 200 °C possessed the highest photocurrents because of the formation of porous structure. Rise and fall times of SnSe-based photodetector decay systematically with increasing growth temperature and the maximum responsivity and detectivity were found to be 3.33 × 10⁻¹ A/W and 2.03 × 10⁷ Jones, respectively for the device employing the film deposited at 200 °C.