Selenium oxide based laser sensors designed for optoelectronic applications

Abstract

In this study, stacked layers of p− SeO2 and p− SiO2 were formed onto n− type silicon wafers to act as laser photosensors. The p− type stacked layers were fabricated using the thermal evaporation technique under a vacuum pressure of 10–5 mbar. Ag and Au thin films were used as Schottky contacts for p− SiO2 and n− Si, respectively. The energy band diagram of the device showed the presence of large conduction and valence band offsets that were sufficient for electron–hole separation. Practical tests using current–voltage characteristics indicated that in the dark, current transport was mostly dominated by diffusion and Richardson Schottky types of current conduction. These transport mechanisms led to a biasing-dependent rectification ratio, which increased by more than 149 times, 24 times, and ~ 4 times under laser lights of wavelengths of 632 nm, 850 nm, and 1550 nm, respectively. The photosensors achieved high current responsivity (R˜ ) and external quantum efficiency (EQE %) reaching 0.54 A/W and 27.5%, respectively, under 632 nm-laser illuminations. The photosensors also showed acceptable values of R˜ and EQE % when irradiated with laser lights of wavelengths of 850 nm and 1550 nm. The proposed devices exhibited features such as a rectification ratio up to 104 and specific detectivity of ~ 1010 Jones under laser light, making them suitable for wireless communication technology.