Self-driven, stable broadband photodetector based on GaAs:CdS heterojunction with ultrahigh on/off ratio and detectivity

In this study, a CdS film was successfully coated on GaAs wafer by the facile and easy method of close-spaced sublimation and a high performance visible-UV-IR, self-driven GaAs:CdS photodetector was obtained. Morphological and elemental analysis of the CdS film was performed by SEM, XRD and EDAX, respectively. The fabricated device exhibited an excellent rectification ratio of 4.90x10(7) in the dark, at +/- 2 Vs. Furthermore, GaAs:CdS photodetector showed a superior photoresponse at zero bias, both in visible and in the UV and IR regions, due to the built-in electrical potential. The maximum photodetector parameters of the fabricated heterojunction in visible light were R = 16.91 mA/W (150 mW, V= -2.0 V), D*=8.99x10(12) (150 mW, V = 0.0 V) Jones and on/off ratio = 4.27x10(5) (V = 0.0 V). Furthermore, R = 0.107 A/W (365 nm), R = 0.083 A/W (395 nm), R = 0.104 A/W (850 nm) were obtained at V= -2.0 Volts, while D* values of 1.972x10(13) Jones (365 nm), 1.566x10(13) Jones (395 nm), and 1.972x10(13) Jones (850 nm) were determined for V = 0.0 Volts. Furthermore, the on/off ratios determined for 365 nm, 395 nm and 850 nm, were 1.79x10(5), 1.43x10(5) and 1.54x10(5), respectively at V = 0.0 V. In addition, after about 40 days, almost no significant degradation of the GaAs:CdS photodetector performance was observed.