Effect of dimensional parameters on the current of MSM photodetector

In this work, we present the influence of dimensional parameters on dark current and photocurrent of the metal–semiconductor–metal photodetector (MSM). MSM photodetectors of different sizes have been fabricated on GaAs (NID). The active area of MSM samples varies between 1×1μm2 and 10×10μm2 with equal electrodes spacing and finger widths (l=D) varying between 0.2 and 1μm. The I(V) characterization in inverse and direct polarization in darkness shows good symmetry of curves, which shows the good performance of components and successful fulfillment of the Schottky contacts. The application of laser fiber of incident light power of 16mW at wavelength of 850nm for the illumination of the MSM photodetectors showed the evolution of the photocurrent ranging from 0.75 to 1.81mA, respectively, for 1 to 0.2μm electrodes spacing at 3V and active area S=3×3μm2. We showed also that variation ranging from 0.45 to 2.5mA, respectively, for S=1×1μm2 to S=10×10μm2 at 3V and 0.3μm electrodes spacing. The resistance of MSM photodetectors obtained evolved proportionally to the electrodes spacing (0.87kΩ for D=0.2μm and 2.27kΩ for D=1μm with S=3×3μm2) and inversely proportional to the surface area (2.02kΩ for S=1×1μm2, and 0.56kΩ for S=10×10μm2 with 0.3μm inter electrodes spacing). ► Good technological realization of MSM photodetectors on GaAs (NID). ► Typical DC characteristics of MSM photodiodes were obtained. ► Breakdown voltage vs. electrodes spacing are presented. ► Evolution of the photocurrent versus bias voltage is presented. ► Variation of MSM resistance vs. surface area for different electrode spacing.