Optical and electrical properties of obliquely deposited a-GeSe2 films

Oblique deposition and exposure to photons of energy greater than the bandgap have a marked effect on the structure and consequently on electrical and optical properties of amorphous chalcogenides. This paper presents a detailed study of photoinduced effect and oblique deposition effect on electrical and optical properties of a-GeSe2 films deposited at different angles (0 degrees-80 degrees). The indirect-optical bandgap energy (2.18 eV) was found to be independent of angle of incidence. The spectral response of refractive index and extinction coefficient has been determined in the wavelength range of 0.6-1 mu m using the transmission spectra. Refractive index decreases with the increase in angle of incidence. The value of refractive index was observed to be 2.28 for 0 degrees and 2.00 for 80 degrees films at 0.646 mu m. An increase in bandgap was also observed on exposure to the UV light for similar to 120 min. The change in bandgap became more significant with the increase in angle of incidence (-2.3% for 0 degrees and similar to 10.6% for 80 degrees). The temperature dependence of conductivity along with time dependence and spectral response of photocurrent has also been investigated.